RMAN restore as encrypted

There is a new feature that was added to 12.2 of RMAN that allows you to restore tablespaces or a whole database "AS ENCRYPTED" or "AS DECRYPTED".

There is documentation of this feature here for 18c, but for some reason it isn't mentioned as a new feature for 12.2, or documented in 12.2.

Now I am going to demonstrate how to use this.

I have a database (bsg) which is a 12.2 database. I have created an encryption wallet, but none of the datafiles are encrypted.
You can see this from the dba_tablespaces view.

[oracle@oracle-server BSG]$ sqlplus

SQL*Plus: Release 12.2.0.1.0 Production on Mon Apr 8 15:37:52 2019

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Enter user-name: / as sysdba

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL>  select tablespace_name,encrypted from dba_tablespaces;

TABLESPACE_NAME                ENC
------------------------------ ---
SYSTEM                         NO
SYSAUX                         NO
UNDOTBS1                       NO
TEMP                           NO
USERS                          NO

SQL>

Now I ran a Full backup of my database

[oracle@oracle-server BSG]$ rman

Recovery Manager: Release 12.2.0.1.0 - Production on Mon Apr 8 14:43:50 2019

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

RMAN> connect target /

connected to target database: BSG (DBID=589892482)

RMAN> backup incremental level 0 database;

I have a full backup and now I am going to restore the tablespace users as encrypted.
NOTE : I am using "RESTORE TABLESPACE xxx AS ENCRYPTED";

[oracle@oracle-server BSG]$ rman

Recovery Manager: Release 12.2.0.1.0 - Production on Mon Apr 8 14:43:50 2019

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

RMAN> connect target /

connected to target database: BSG (DBID=589892482)

RMAN> alter tablespace users offline;

Statement processed

RMAN> restore tablespace users as encrypted;

Starting restore at 04/08/19 14:53:22
using channel ORA_DISK_1

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00007 to /home/oracle/app/oracle/oradata/BSG/datafile/o1_mf_users_fz01zl49_.dbf
channel ORA_DISK_1: reading from backup piece /home/oracle/app/oracle/fast_recovery_area/bsg/BSG/backupset/2019_04_08/o1_mf_nnnd0_TAG20190408T144422_gbq5n71p_.bkp
channel ORA_DISK_1: piece handle=/home/oracle/app/oracle/fast_recovery_area/bsg/BSG/backupset/2019_04_08/o1_mf_nnnd0_TAG20190408T144422_gbq5n71p_.bkp tag=TAG20190408T144422
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
Finished restore at 04/08/19 14:53:23
RMAN> recover tablespace users;

Starting recover at 04/08/19 14:53:44
using channel ORA_DISK_1

starting media recovery
media recovery complete, elapsed time: 00:00:00

Finished recover at 04/08/19 14:53:44

RMAN> alter tablespace users online;

Statement processed

RMAN> exit

Now that I restored the tablespace and recovered it let's see if it is encrypted in the catalog.

[oracle@oracle-server BSG]$ sqlplus

SQL*Plus: Release 12.2.0.1.0 Production on Mon Apr 8 14:54:13 2019

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Enter user-name: / as sysdba

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> select tablespace_name,encrypted from dba_tablespaces;

TABLESPACE_NAME                ENC
------------------------------ ---
SYSTEM                         NO
SYSAUX                         NO
UNDOTBS1                       NO
TEMP                           NO
USERS                          YES

Now to backup the tablespace.  Since it is newly encrypted, I need to make sure I perform a new Level 0 incremental backup to capture the encrypted datafiles.

[oracle@oracle-server datafile]$ rman

Recovery Manager: Release 12.2.0.1.0 - Production on Mon Apr 8 16:12:08 2019

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

RMAN> connect target /

connected to target database: BSG (DBID=589892482)

RMAN> backup incremental level 0 tablespace users;

Starting backup at 04/08/19 16:12:25
using target database control file instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=265 device type=DISK
channel ORA_DISK_1: starting incremental level 0 datafile backup set
channel ORA_DISK_1: specifying datafile(s) in backup set
input datafile file number=00007 name=/home/oracle/app/oracle/oradata/BSG/datafile/o1_mf_users_fz01zl49_.dbf
channel ORA_DISK_1: starting piece 1 at 04/08/19 16:12:26
channel ORA_DISK_1: finished piece 1 at 04/08/19 16:12:27
piece handle=/home/oracle/app/oracle/fast_recovery_area/bsg/BSG/backupset/2019_04_08/o1_mf_nnnd0_TAG20190408T161226_gbqbsbmv_.bkp tag=TAG20190408T161226 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:01
Finished backup at 04/08/19 16:12:27

Starting Control File and SPFILE Autobackup at 04/08/19 16:12:27
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03009: failure of Control File and SPFILE Autobackup command on ORA_DISK_1 channel at 04/08/2019 16:12:28
ORA-00237: snapshot operation disallowed: control file newly created

Now the backup was successful, but the autobackup of the controlfile failed.

There is a MOS note on this (Doc ID 2320446.1)

You cannot backup the controlfile until the database is bounced because there is a data dictionary check pending.  Once I bounce the database all is good.

Now now let's try it the other way..

RESTORE TABLESPACE xxx AS DECRYPTED;

[oracle@oracle-server trace]$ rman

Recovery Manager: Release 12.2.0.1.0 - Production on Mon Apr 8 16:29:30 2019

Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.

RMAN> connect target /

connected to target database: BSG (DBID=589892482)

RMAN> alter tablespace users offline;

using target database control file instead of recovery catalog
Statement processed

RMAN> restore tablespace users as decrypted;

Starting restore at 04/08/19 16:29:43
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=265 device type=DISK

channel ORA_DISK_1: starting datafile backup set restore
channel ORA_DISK_1: specifying datafile(s) to restore from backup set
channel ORA_DISK_1: restoring datafile 00007 to /home/oracle/app/oracle/oradata/BSG/datafile/o1_mf_users_fz01zl49_.dbf
channel ORA_DISK_1: reading from backup piece /home/oracle/app/oracle/fast_recovery_area/bsg/BSG/backupset/2019_04_08/o1_mf_nnnd0_TAG20190408T162748_gbqcp4vg_.bkp
channel ORA_DISK_1: piece handle=/home/oracle/app/oracle/fast_recovery_area/bsg/BSG/backupset/2019_04_08/o1_mf_nnnd0_TAG20190408T162748_gbqcp4vg_.bkp tag=TAG20190408T162748
channel ORA_DISK_1: restored backup piece 1
channel ORA_DISK_1: restore complete, elapsed time: 00:00:01
Finished restore at 04/08/19 16:29:45

RMAN> recover tablespace users;

Starting recover at 04/08/19 16:29:54
using channel ORA_DISK_1

starting media recovery
media recovery complete, elapsed time: 00:00:00

Finished recover at 04/08/19 16:29:54

RMAN> alter tablespace users online;

Statement processed

RMAN>

Finally let's double check.

[oracle@oracle-server trace]$ sqlplus

SQL*Plus: Release 12.2.0.1.0 Production on Mon Apr 8 16:31:15 2019

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Enter user-name: / as sysdba

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> select tablespace_name,encrypted from dba_tablespaces;

TABLESPACE_NAME                ENC
------------------------------ ---
SYSTEM                         NO
SYSAUX                         NO
UNDOTBS1                       NO
TEMP                           NO
USERS                          NO

ZDLRA - Space management

When backing up to a ZDLRA you want to optimize  your storage allocation to ensure each database can meet its recovery window goal.

You also want to make sure that the ZDLRA doesn't needs to aggressively reclaim space.

***  NOTE - This was updated on 9/13/19 as I've learned more.

Values you can set to control space and purging

Mandatory values

• Recovery Window Goal (RWG) - How far back (in days) do I need to ensure a point in time recovery for my databases. This is set at the policy level.

        ** NOTE. This is a GOAL, not a guarantee.

• Disk Reserved Space - How much storage to I need to ensure I keep my recovery window goal for this database.    This is set at the database level and should be adjusted as the database grows.  The sum of Disk_Reserved_Space for all databases can not be greater than the amount of space available on the storage location.  

Optional values

• Max_Retention_Window -  What is the maximum number of days I want to keep backups for.  The MOS note on purging does a great job of documenting what the recommended value is (if you want to set it), and what the current default value is based on RA version.

• Guaranteed_Copy -  This is set at the policy level and has 2 possible values
• NO (default) - Follow purge rules regardless if backups have been replicated to tape/downstream.
• YES - Backups that have not been successfully copied to tape/replicated are NOT eligible for deletion.  If the space usage for the database is above the Disk_Reserved_Space, incoming backups (both through RMAN and real-time redo) will be rejected.

Derived values that control space and purging

Each storage location has the following values that are used to control purging.

• Free_Space - The amount of space (GB) that is available for storing backups . This is for the storage location

• Free_Space_Goal - The estimated amount of space that is needed to support incoming backups to the storage location. This is evaluated every 3 hours. This estimate is the sum of space needed for the next 6 hours taking into account 2 types of incoming backups .
• Daily backups from databases that have historical data.  The amount of space required to support normal incoming backup space is calculated in the Free_Space_Goal.
• Newly added databases. In the case of databases that do not have good historical data, the Disk_Reserved_Space is used to calculate how much space needs to be available to support incoming backups.
• Recovery_Window_Space - The amount of space needed by the database to support the RWG. This is available for each database.
• Space_Usage - The amount of space currently being used by this protected database

Purge Process

How backups are prioritized for purging is described in this MOS note.

Zero Data Loss Recovery Appliance Purging Rules (Doc ID 2353188.1)

There are 3 rules of purging and this is outlined in the MOS note.

• Rule 1 - This is the normal housekeeping purging and occurs on a regular basis for all databases.  Any backups whose recovery window is greater than the Max_Retention_Window are periodically removed from the ZDLRA to make space for incoming backups. This is a low priority background process.

The way this rule works is that the retention window for each database (maximum based on policy) grows until the number of days set for Max_Retention_Window is reached for the database.  When this occurs, the retention period is purged down to the Recovery_Window_goal for that database.  For example if my database has a Recovery_Window_Goal of  15 days, and a Max_Retention_Window of 20 days, when the database reaches 20 days of retention, the oldest 5 days of backups will be removed and I will have 15 days of backups after purging.  This ensures the purge is more of a bulk process, and ensures that the purge workload is spread out for all databases.

• Rule 2 - When the Free_Space for a storage location falls below the Free_Space_Goal regular purging begins.  The database whose current retention is most above it's RWG is added to the purging queue and purging begins at a low priority process.

The way this rule works is similar to Rule 1.  Beginning with the database with the largest current  number of days of retention beyond the Recovery_Window_goal, databases, each database is purged down to its Recovery_Window_Goal until enough space is released. As I said, the processing is similar to rule 1, except it doesn't wait until the Max_Retention_Window is reached.

     

• Rule 3 - When the Free_Space is not enough  to allow incoming backups, a more aggressive purging begins starting with the database that is most above (by percentage) its allocated Disk_Reserved_Space.  This could impact the RWG if the Disk_Reserved_Space is not large enough to support the RWG.

** NOTE there are a few exceptions to removing backups.

• Any backup that is currently being restored by a client is exempt from the purging rules. THis ensures that any restore in process is successful
• Any replication or copy-to-tape process that is currently executing is exempt.  This ensures that the replication/tape copy completes successfully.

How this works.

As long as there is enough space in the storage location to support the Max_Retention_Window for all databases, there is nothing to note on purging.  Rule 1 executes on a periodic basis.

Rule 2 - Free_Space_Goal.

As I tried to explain above, Free_Space_Goal is a estimate of how much space may be needed to ingest new backups.
If the RA believes that it will need more space available ingest backups than what is currently available, it will start purging older backups that are not needed to support the RWG for databases.
This purging will continue until the Free_Space_Goal is more than Free_Space, or all databases only have backups that support their RWG.

This makes sense for a couple of reasons.

• It takes into account newly added databases that don't have history.  This ensures that when you send the first few backups to the RA, there is sufficient space to ingest these backups.
• If space has become tight on the RA, and it can no longer support the Max_Retention_Window for databases, there is enough space available to keep ingesting new backups.

Rule 2 only goes as far as removing backups that are not needed to support the RWG for all databases.

As you can imagine this might not free enough space if your Disk_Reserved_Space is not adequate for all databases.

Rule 3 - Disk_Reserved_Space

Rule 3 kicks in when you run out of Free_Space.  This is the most aggressive purging, and it's priority is higher than most processes that occur on the ZDLRA.  Accepting incoming backups is one of the highest priorities and freeing up space for backups is critical.

From this document, you can see that this is where the Disk Reserved Space allocation for each database becomes important.

The amount of Disk Reserved Space allocated is compared to the amount of space used by this database.  The % of space used greater than the space reserved is used to decide the order in which databases backups are purged.

Backups will continue to be purged to free up space.  

A good recommendation is to set the Disk_Reserved_Space to at least 10% greater than what is needed to support your RWG. This needs to be updated on a regular basis.

*** NOTE   -- Also, you need to keep in mind that you might have some basis with seasonal peaks, ie cyber Monday.  For databases that have periodic peak periods, the Disk_Reserved_space should reflect the amount of space needed to support the peak.  This should be exempt from any automated adjustment using the RWG needed space.

Keep in mind that the combined Disk Reserved Space for all databases cannot be larger than the amount space available in the storage pool.

Important notes :

It is critical that you accurately set the Disk_Reserved_Space for all databases.  If you consistently set the Disk_Reserved_Space to be 20% greater than what is needed for the RWG for ALL databases, this ensures that the ZDLRA will not get more 80% full, and give you some buffer when space becomes tight.

Incorrectly setting the Disk_Reserved_Space for an existing  database may cause the RWG to be lost.  If the Disk_Reserved_Space is less than what is needed, Rule 3 may purge backups needed to support the RWG to free up space. THE RWG is NOT GUARANTEED.

Correctly setting the Disk_Reserved_Space for newly added databases is important.  This value is used by the Free_Space_Goal, and may force unnecessary purging to make room for the incoming backups.

Adjusting RWG

There is a package you can use to estimate how much storage is needed to support a given recovery window goal.  This is can be used to determine if a databases's reserved space is enough to meet the goal.  DBMS_RA.ESTIMAT_SPACE is the package you call.

ESTIMATE_SPACE

This procedure estimates the amount of storage in GB required for recovery of a given database and a desired recovery window.

Syntax

FUNCTION estimate_space (
   db_unique_name IN VARCHAR2,
   target_window IN DSINTERVAL_UNCONSTRAINED) RETURN NUMBER;

Parameters

Table 12-23 ESTIMATE_SPACE Parameters

Parameter	Description
db_unique_name	The name of the database needing the storage estimate.
target_window	The desired recovery window for the database. Specify the goal as any valid INTERVAL DAY TO SECOND expression, such as INTERVAL '2' DAY (2 days), INTERVAL '4' HOUR (4 hours), and so on.

Recommendations on Purging and Space Management.

• Correctly setting the Disk_Reserved_Space is critical to managing space

• Periodically adjusting the Disk_Reserved_Space as the databases grows or shrinks is important.  This can be done through the PLSQL package, and can be scheduled on a regular basis.

• Know which databases, if any, have seasonal peaks and ensure the Disk_Reserved_Space reflects any peak.

• Properly set the Disk_Reserved_Space for new database.  This will help prevent unnecessary purging, and possibly affecting ingesting of backups.

• Use the estimate space package to adjust Disk_Reserved_Space if adjusting RWG for a policy.

• Create an alert on the Disk_Reserved_Space falling below the Recovery_Window_Space. This tells you that the RWG may be lost if the ZDLRA needs to reclaim space.

• Keep track of the Space_Usage vs Disk_Reserved_Space vs Recovery_Window_Space to understand how each databases space will be managed.

• Periodically check SAR report (MOS note 2275176.1) for issues.  Process issues, etc. that cause ordering waits affect the estimated "needed space for RWG".  This may quickly inflate the Disk_Reserved_space when using an automated process.

• Use the Size_Estimate from the RA_DATABASE view to ensure the space utilization makes sense.  This can be a check to verify that the storage utilization of backups on the ZDLRA seems reasonable for the size of the database.

TDE Implementation first 30 days

This blog post is on the immediate effect of implementing TDE in your database backup storage.

In the last blog post I mentioned that after implementing TDE you need to explicitly perform a full backup on all tablespaces you encrypt.

• If you are performing an incremental strategy (level 0 and level 1) then explicitly perform a level 0 backup.
• If you are using an incremental merge backup (BACKUP INCREMENTAL LEVEL 1 for RECOVERY of COPY), you must create a new image copy and start a new divergent backup

The reason a full explicit backup is needed is that the SCN number of the underlying data blocks do not change when you implement encryption.  Because of this, any backup strategy you are using does not recognize that the the blocks have changed.  This is true even with the ZDLRA.

Above is the reason for this post.  If you have an unencrypted database, and you implement TDE on all tablespaces, then perform a full backup of all tablespaces, you will have 2 copies of your backups for a period of time.

I am going to take a closer look at what this means to my backup storage when implementing TDE.

For my example, I'm going to use the same example I used in the last post.

Below is what it looks like.

Using my example dataset for a just a weekly full backup and a daily incremental backup (using deduplication) you can see that

The data in my database is 35 GB ( the fully allocated size is 50 GB).
The amount of change over 30 days is 70 GB.
Compressing both of these, the final size is 41.5 GB used.

Prior to implementing TDE, I am using 41.5 consistently to store 30 days of compressed backups for my 50GB database.

The next column shows what happens when after implementing TDE.  The full backup size compressed is now 43.9 GB and the amount of change over 30 days is 54 GB compressed.
After implementing TDE, I am using 97.9 GB consistently to store 30 days of compressed backups for my 50 GB database.

Now let's see what first 30 days looks like.

This shows the unencrypted backups (purple) and how they start to age off and get removed on day 31.  You can also see how the encrypted backups (gray) grow over time and the will stabilize to the size you see on day 31.

You can see that there is an immediate impact to the backup usage. That growth continues until the old backup is finally ages off.

You need to plan for TDE ahead of time.  For my example dataset, the storage needed more than doubled.

Implementing TDE

This blog post is about what happens when you implement TDE (Transparent Data Encryption) in your database.

I started with 2 other blog posts, but I soon realized that this is a HUGE topic with ramifications throughout the database system.

Well let's start at the beginning.
I wanted to know what happens when you implement TDE.
The 3 items that I keep hearing are

1. Encrypted data will not compress
2. Encrypted data will not dedupe
3. Implementing Advanced compression in the database will mitigate the loss of compression to encryption by compressing the data before encrypting

Now in order to investigate this further, I had some restrictions that affected my testing.

• I had no access to a deduplicating appliance to test point 2
• I didn't have a real data set to use.  I ended up using the SOE schema in swingbench 
• The only way I could test the effect of compression was to compress the backupset.  Most appliances (including the ZDLRA) break the file up into pieces and compress each piece. I couldn't emulate the affect of doing that.

Now for my testing dataset.  I created a dataset in the SOE tablespace that in uncompressed.  I then took that dataset and created a second copy of the schema with advanced compression in place in the SOE_COMPRESSED tablespace.

When I finished this I had 2 tablespaces comprised of 10 x 5 GB datafiles.

SOE                              --> uncompressed copy of data

SOE_COMPRESSED --> Advanced compression (ACO) copy of data

In the graphs above you can see  that out of the 50 GB of allocated space
uncompressed  --> 35.8 GB of used space
compressed      -->  24.9 GB of used space

These are the datasets I am going to use throughout my testing.

I started by taking these 2 datasets and seeing what happens with the 2 full backup types
L0               --> Full backups saved as backupset
image copy --> Full copy of datafile.

Below is what I found when I compressed both these backup types.

This was very helpful to see what happens.

For my uncompressed dataset (35 GB), I was able to compress the file down to 20 GB.
For my uncompressed image copy (35 GB used) I was able to compress the file down to 18 GB
For my compressed dataset (24 GB), I was able to compress the file down to 18 GB
For my compressed image copy (24 GB), I was able to compress the file down to 18 GB.

So what I learned is no matter how I compressed the data, in the database (ACO), or just compress the backup, the final size is still ~18 GB.

Now we have some benchmarks on what happens when I just compress the backups.

I started with encrypting the image copy.  This was one area that I wanted to learn more about for 2 reasons.

1. Many of the newer backup strategies use the "incremental merge" process that started with 10G of oracle. I was curious what happens to image copies when you implement TDE.
2. Many of the Flash arrays use compression to get more usable storage from the smaller SSD drives.  Looking at what happens with compressing the datafile copies gives a lot of insight into how those flash arrays will be affected by TDE.

You can see from the above testing there was a very significant impact on the compressed size of the image copy.  Both compressed and uncompressed data compressed nicely when it was unencrypted.  After encrypting the dataset, the compressed size is about 3x larger than the compressed size.

This gives me the answer on how it will affect these 2 areas.

1. If using an "incremental merge" based backup that is stored on compressed storage, you will need 3x the amount of storage for your backups.
2. If using Flash storage for your database files that utilizes compression, you will need 3x the amount of database storage.

OK.. There's the first answer I was looking for.

Now let's see what happens with my Level 0 backups.

With level 0 backups, I can see the benefit of compressing the data first.

I can also see the effect of encryption.

Compressing the data first saved me a about a 1/3 of the size of the data, and about 1/3 of the size of the backupset compressed (once encrypted).

Now let's take a look of the effect of encryption on the change rate.  I updated one of the tables in the database to create a change rate, and I looked at both the archive logs and the incremental backup.

Wow.. What stood out to me on this testing is the size of the archive logs.  Adding Advanced Compression to the database decreased the size of the incremental backups (expected), but increased the size of the archive logs.  Then when I looked at the compressed size (both with and without encryption) compressing the data in the database increased the size of the archive logs.

This showed me a lot of what happens with TDE.  What I learned through this was.

1. Encrypted data indeed does not compress, in fact it can get much bigger.
2. Implementing Advanced Compression does not always mitigate the effects of encryption. Depending on the dataset, it might have very limited effect.
3. The compressed size of datafiles and image copy backups may increase by 3x or more depending on the amount of free space you typically have in your datafiles..

Verifying you have a recoverable backup

As you probably know the best way to validate that you can recover your database to a specific point-in-time is to perform a point-in-time recovery of the database and successfully open it. That isn't always possible due to the size of the database, infrastructure necessary, and the time it takes to go through the process.  To verify recoverability there are several commands that give you all the pieces necessary, but it is important to understand what each command does.

Restore Validate -  The restore validate command can be performed for any database objects including the whole database to verify the files are valid.  This command can be used to restore as of the current time (default), but you can also specify a previous point-in-time.  The validate verifies that the files are available and also checks for corruption.  By default it checks for physical corruption, but it can also check for logical corruption. This command reads through the backup pieces 

Examples of restore validate for different cases.

verify current backup -

RMAN> RESTORE DATABASE VALIDATE;

RMAN> RESTORE ARCHIVELOG ALL VALIDATE;

This will verify that the last full backup (level 0) does not contain corruption, and it verifies that archivelogs exist throughout the recovery window, and that they do not contain corruption. 

verify previous backup -

RMAN> RESTORE DATABASE VALIDATE UNTIL TIME "to_date('xx/xx/xx xx:xx:xx','mm/dd/yy hh24:mi:ss')";

This will verify that the full backup performed prior to the "until time" is available and does not contain corruption.

Restore Preview - The restore preview can be used to identify the backup pieces necessary for a restore AND recovery of the database.  The preview will show all the datafile backups (both full and incremental), along with the archive logs needed.  The restore preview does not check for corruption, it simply lists the backup pieces necessary.

Validate -  The validate command can be performed on any database objects along with backupsets. Unlike restore, you cannot give it an "until time", you must identify the object you want to validate.  By default it checks for physical corruption, but it can also check for logical corruption.

It is critical to understand exactly what all three commands do to ensure you can efficiently recover to a previous point-in-time.  It takes a combination of 2 commands (plus an extra to be sure).

So let's see how I can test if I can recover to midnight on the last day of the previous month.  My backup strategy is "Weekly full/Daily incremental" backups.  I perform my full backups on Saturday night and keep my backups for 90 days. My archive logs are kept on disk for 20 days.

It is now 12/15/18 and I want to verify that I can recover my database to 23:59:59 on 11/30.

First I want to perform a restore validate of my database using until time.

RMAN > restore validate database UNTIL TIME "to_date('11/30/18 23:59:59','mm/dd/yy hh24:mi:ss')";
By looking through the logs, I can see the this command performed a validation of the Level 0 (full) backup I performed on 11/24/18.  It did not validate any of the incremental backups or archive logs that I will need to recover the database.

Now I want to perform a restore validate of my archive logs using until time.
RMAN > restore validate archivelog UNTIL TIME "to_date('11/30/18 23:59:59','mm/dd/yy hh24:mi:ss')";
By looking through the logs, I can see that this command validated the backup of all my older archive logs (older than 20 days), and it validated the FRA copy of my archive logs that were 20 days or newer.
There are couple of issues with this that jump out at me.

1) My incremental backups are NOT validated.  Yes I know I can recover to the  point-in-time I specified, but all I verified is that it is possible by applying 6 days of archive logs.

2) I don't know if any of my newer backups of archive logs are corrupt.  The validation of archive logs only validated backups of archivelogs that are NOT on disk. I still need to validate the archive log backups for archive logs that will age off from the FRA in a few days to be sure..

3) The process doesn't check or validate a backup of the controlfile.  If I am restoring to another server (or if I lose my database completely) I want to make sure I have a backup of the controlfile to restore.

The only way to be sure that I have an efficient, successful recovery to this point in time is to combine the 2 commands and use that information to validate all the pieces necessary for recovery.
Here are the steps to ensure I have valid backups of all the pieces necessary to restore efficiently.

1) Perform a restore preview and write the output to a log file.

2) Go through the output from step 1 and identify all the "BS KEY" (backupset key) values.

3) Perform a "validate backupset xx;" using the keys from step 2 to ensure all datafile backups (both full and incremental backups) are valid.

4) Go through the output from step 1 and identify the archive log sequences needed.

5) Identify the backupsets that contain all log sequences needed (my restore preview pointed to the archive logs on disk).

6) Perform a "validate backupset xx;" using the keys from step 5.

7) Perform a restore controlfile to a dummy location using the UNTIL time.

As you can see the "restore validate" is not enough to ensure efficient recovery. It only ensures that the you have a valid RESTORE not a valid recovery.
The ZDLRA does constant recovery checks using the virtual full backups, and archive logs.
The ZDLRA ensures you can quickly AND successfully recover to any point-in-time within your retention window.

TDE–How to implement TDE in your database and what to think about (part 2)

This is the second part in a series on implementing TDE and what happens to the sizing.

At first my plan was to encrypt the dataset I created in my first post, but instead I compressed it.

At this point (and throughout this post), I am working with an un-encrypted dataset.

One of the first things to understand about Encryption is that encrypted data DOES NOT compress.
This is critical when understanding what happens when you implement TDE.

One way to save storage when implementing TDE is to implement encryption AND compression together.

In order to break down the affects of encryption on compressed data VS uncompressed data, I took my dataset (the SOE dataset from swing bench) and I compressed it.  I implemented Advanced compression on the tables, and I compressed the indexes and rebuilt them.

I now have 2 copies of the same dataset. 1 is compressed, and 1 is not.

Now let's take a look at the sizing of the Data sets and I will go through the same backup procedures and see what happens.

SEGMENT_NAME              SEGMENT_TYPE Space Used uncompressed   Space Used Compressed SPACE_SAVINGS
------------------------- ------------ ------------------------- -------------------- -------------
ADDRESSES                 TABLE           3,392 MB                  3,264 MB                      3
ADDRESS_CUST_IX           INDEX             703 MB                    728 MB                     -3
ADDRESS_PK                INDEX             662 MB                    888 MB                    -34
CARDDETAILS_CUST_IX       INDEX             703 MB                    562 MB                     20
CARD_DETAILS              TABLE           2,048 MB                  1,600 MB                     21
CARD_DETAILS_PK           INDEX             662 MB                      0 MB                    100
CUSTOMERS                 TABLE           3,328 MB                  2,880 MB                     13
CUSTOMERS_PK              INDEX             443 MB                      0 MB                    100
CUST_ACCOUNT_MANAGER_IX   INDEX             417 MB                    272 MB                     34
CUST_DOB_IX               INDEX             528 MB                    280 MB                     47
CUST_EMAIL_IX             INDEX             975 MB                    280 MB                     71
CUST_FUNC_LOWER_NAME_IX   INDEX             683 MB                    280 MB                     58
INVENTORIES               TABLE             176 MB                    176 MB                      0
INVENTORY_PK              INDEX              18 MB                      0 MB                    100
INV_PRODUCT_IX            INDEX              16 MB                     12 MB                     24
INV_WAREHOUSE_IX          INDEX              16 MB                     12 MB                     24
ITEM_ORDER_IX             INDEX           2,000 MB                  1,770 MB                     11
ITEM_PRODUCT_IX           INDEX           1,768 MB                  1,301 MB                     26
LOGON                     TABLE           1,728 MB                  1,728 MB                      0
ORDERENTRY_METADATA       TABLE               0 MB                      0 MB                      0
ORDERS                    TABLE           3,968 MB                  2,816 MB                     29
ORDER_ITEMS               TABLE           6,976 MB                  4,992 MB                     28
ORDER_ITEMS_PK            INDEX           2,234 MB                      0 MB                    100
ORDER_PK                  INDEX             632 MB                      0 MB                    100
ORD_CUSTOMER_IX           INDEX             671 MB                    480 MB                     28
ORD_ORDER_DATE_IX         INDEX             752 MB                    439 MB                     41
ORD_SALES_REP_IX          INDEX             594 MB                    438 MB                     26
ORD_WAREHOUSE_IX          INDEX             709 MB                    438 MB                     38
PRD_DESC_PK               INDEX               0 MB                      0 MB                    100
PRODUCT_DESCRIPTIONS      TABLE               0 MB                      0 MB                      0
PRODUCT_INFORMATION       TABLE               0 MB                      0 MB                      0
PRODUCT_INFORMATION_PK    INDEX               0 MB                      0 MB                    100
PROD_CATEGORY_IX          INDEX               0 MB                      0 MB                      0
PROD_NAME_IX              INDEX               0 MB                      0 MB                      0
PROD_SUPPLIER_IX          INDEX               0 MB                      0 MB                   -100
WAREHOUSES                TABLE               0 MB                      0 MB                      0
WAREHOUSES_PK             INDEX               0 MB                      0 MB                    100
WHS_LOCATION_IX           INDEX               0 MB                      0 MB                   -100

Here is the total savings by compressing both tables and indexes with advanced compression.

Space Used uncompressed   Space Used Compressed  SPACE_SAVINGS
------------------------- ---------------------- -------------
  36,804 MB                 25,636 MB                       30

Now to compare this with the previous data uncompressed I am going to backup by tablespace.  Below is the sizing of the backups. I used a tag to identify the backups.

-rw-rw----. 1 oracle oracle 26773323776 Nov 29 17:02 COMPRESSED_SOE.bkp
-rw-rw----. 1 oracle oracle 38441140224 Nov 29 17:04 UNCOMPRESSED_SOE.bkp
-rw-rw----. 1 oracle oracle 10987765760 Nov 29 18:35 BASIC_COMPRESSED_SOE.bkp
-rw-rw----. 1 oracle oracle 11135655936 Nov 29 18:36 BASIC_COMPRESSED_SOE_COMPRESSED.bkp
-rw-rw----. 1 oracle oracle 13360308224 Nov 29 20:12 MEDIUM_COMP_SOE_COMPRESSED.bkp
-rw-rw----. 1 oracle oracle 14383603712 Nov 29 20:12 MEDIUM_COMPRESSED_SOE_.bkp
-rw-rw----. 1 oracle oracle  9420791808 Nov 30 00:12 HIGH_COMP_SOE_COMPRESSED.bkp
-rw-rw----. 1 oracle oracle  9112944640 Nov 30 00:23 HIGH_COMPRESSED_SOE.bkp

Now I'm going to put that in a table and a chart to compare..

First the table of sizes

Now the chart

Now by looking at the chart it is apparent what happens with compression and the data.

• Compression in the database reduced the size of the data by 30%
• An uncompressed backupset matched the size of the data
• Once I compressed the backupset, the difference is size was minimal.

** Bottom line - Compressing the data in the database saved on the uncompressed backupsize. Once the backupset is compressed the final size is about the same.

** Final conclusion -- Most modern backup appliances (ZDLRA, ZFS, DD) compress the backups.  When using those appliances with unencrypted data, the final size is the same regardless of whether the data is compressed in the Database.

Now that I've looked at both compressed and uncompressed data at the DB and backupset I am going to compress the data.  Next post.

TDE–How to implement TDE in your database and what to think about (part 1)

This is the first part in a series of blog posts on TDE.
Many organizations are moving to TDE, and this can have a dramatic affect on your systems.
TDE impacts 2 areas
1) Post encryption compression goes away.  Encrypted data can’t be compressed.  Now why do I mention “Post encryption” ? This is because data can be compressed before encrypting.  Compressed data in your database (HCC, OLTP, basic etc.) is compressed PRIOR to encryption.  Utilizing compression in your database not only saves you disk space on your storage system, but it also saves you disk space for your backups.  The loss of compression post encryption can have many consequences you might not immediately think of

• if you are using SSD storage that compresses blocks, you need to take into account the extra storage needed
• If you are using a De-duplication appliance you will lose most of the benefits of de-duplication.
• If you are compressing your backups, you will lose the benefits gained from compression (small backups and lowered network traffic).

2) Moving to TDE requires more space during the migration. Rebuilding the tablespaces with a newly encrypted copy is done by creating a second copy of each datafile (encrypted), and then removing the pre-encrypted copy.  The database switches to the new datafile when the process is complete.  This utilizes additional storage for the second copy of the datafiles.  The other migration impact is an increase in backup storage.  After encrypting tablespaces, a new level 0 backup is needed to ensure you are restoring to an encrypted copy of the data. Remember the encryption process changes all the blocks in the datafiles. I will discuss the backup implications more later.

Now I’m going to start by describing the dataset I used for testing.
In order to create this dataset I used the oewizard from Swingbench

Here are the objects and the sizes.

SEGMENT_NAME              SEGMENT_TYPE TABLESPACE_NAME SPACE_USED
------------------------- ------------ --------------- ------------
ADDRESSES                 TABLE        SOE                3,392 MB
ADDRESS_CUST_IX           INDEX        SOE                  703 MB
ADDRESS_PK                INDEX        SOE                  662 MB
CARDDETAILS_CUST_IX       INDEX        SOE                  703 MB
CARD_DETAILS              TABLE        SOE                2,048 MB
CARD_DETAILS_PK           INDEX        SOE                  662 MB
CUSTOMERS                 TABLE        SOE                3,328 MB
CUSTOMERS_PK              INDEX        SOE                  443 MB
CUST_ACCOUNT_MANAGER_IX   INDEX        SOE                  417 MB
CUST_DOB_IX               INDEX        SOE                  528 MB
CUST_EMAIL_IX             INDEX        SOE                  975 MB
CUST_FUNC_LOWER_NAME_IX   INDEX        SOE                  683 MB
INVENTORIES               TABLE        SOE                  176 MB
INVENTORY_PK              INDEX        SOE                   18 MB
INV_PRODUCT_IX            INDEX        SOE                   16 MB
INV_WAREHOUSE_IX          INDEX        SOE                   16 MB
ITEM_ORDER_IX             INDEX        SOE                2,000 MB
ITEM_PRODUCT_IX           INDEX        SOE                1,768 MB
LOGON                     TABLE        SOE                1,728 MB
ORDERENTRY_METADATA       TABLE        SOE                    0 MB
ORDERS                    TABLE        SOE                3,968 MB
ORDER_ITEMS               TABLE        SOE                6,976 MB
ORDER_ITEMS_PK            INDEX        SOE                2,234 MB
ORDER_PK                  INDEX        SOE                  632 MB
ORD_CUSTOMER_IX           INDEX        SOE                  671 MB
ORD_ORDER_DATE_IX         INDEX        SOE                  752 MB
ORD_SALES_REP_IX          INDEX        SOE                  594 MB
ORD_WAREHOUSE_IX          INDEX        SOE                  709 MB
PRD_DESC_PK               INDEX        SOE                    0 MB
PRODUCT_DESCRIPTIONS      TABLE        SOE                    0 MB
PRODUCT_INFORMATION       TABLE        SOE                    0 MB
PRODUCT_INFORMATION_PK    INDEX        SOE                    0 MB
PROD_CATEGORY_IX          INDEX        SOE                    0 MB
PROD_NAME_IX              INDEX        SOE                    0 MB
PROD_SUPPLIER_IX          INDEX        SOE                    0 MB
WAREHOUSES                TABLE        SOE                    0 MB
WAREHOUSES_PK             INDEX        SOE                    0 MB
WHS_LOCATION_IX           INDEX        SOE                    0 MB


TOTAL                                                                                 36,804 MB

Here is the total size for the data

TABLESPACE_NAME   FILE_ID FILE_NAME            SPACE_USED   TOTAL_ALLOCATED
--------------- --------- -------------------- ------------ --------------------
SYSTEM                  1 system01.dbf              819 MB       830 MB
SYSAUX                  3 sysaux01.dbf              809 MB       860 MB
UNDOTBS1                4 undotbs01.dbf             369 MB    29,180 MB
SOE                     5 soe_1.dbf               3,600 MB     5,120 MB
USERS                   7 users01.dbf                 5 MB         5 MB
SOE                     8 soe_2.dbf               3,841 MB     5,120 MB
SOE                     9 soe_3.dbf               3,822 MB     5,120 MB
SOE                    10 soe_4.dbf               3,825 MB     5,120 MB
SOE                    11 soe_5.dbf               3,806 MB     5,120 MB
SOE                    12 soe_6.dbf               3,728 MB     5,120 MB
SOE                    13 soe_7.dbf               3,781 MB     5,120 MB
SOE                    14 soe_8.dbf               3,442 MB     5,120 MB
SOE                    15 soe_9.dbf               3,464 MB     5,120 MB
SOE                    16 soe_10.dbf              3,495 MB     5,120 MB


===================================================================================================================

Total                                   38,303 MB      60,820 MB      22,517 MB

From above I can see that I am using 38 GB of space, out of the 61 GB of space allocated.
Now I created a backup set . With no compression the size of the backup set is about the size data used.

[oracle@oracle-server]$ ls -al
total 38910628
drwxrwx---. 2 oracle oracle          58 Nov 15 16:34 .
drwxrwx---. 3 oracle oracle          24 Nov 15 16:23 ..
-rw-rw----. 1 oracle oracle 39844478976 Nov 15 16:37 o1_mf_nnnd0_TAG20181115T163432_fyvsm8rz_.bkp
[oracle@oracle-server]$

Just to save my spot .I’m going to create a restore point to make this the starting point of all my testing.

SQL> create restore point new_database;

Restore point created.

Now let’s look at what happens when I compress the backup of this database

 oracle oracle 39844478976 Nov 15 16:37 o1_mf_nnnd0_TAG20181115T163432_fyvsm8rz_.bkp   ---> Original backup
 oracle oracle 11424759808 Nov 15 17:09 o1_mf_nnndf_TAG20181115T165247_fyvtoj7m_.bkp   ---> Basic Compression
 oracle oracle  9468592128 Nov 15 18:33 o1_mf_nnndf_TAG20181115T174452_fyvxq4s2_.bkp   ---> High Compression
 oracle oracle 14488240128 Nov 15 18:44 o1_mf_nnndf_TAG20181115T183319_fyw0l08k_.bkp   ---> Medium Compression

Finally I took an incremental merge backup to see what happens with that.

ls -al
total 62300276
drwxrwx---. 2 oracle oracle       4096 Nov 16 09:47 .
drwxrwx---. 7 oracle oracle         92 Nov 14 13:24 ..
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:38 o1_mf_soe_fyxolco8_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:39 o1_mf_soe_fyxon2o4_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:40 o1_mf_soe_fyxoohtl_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:41 o1_mf_soe_fyxopwy8_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:41 o1_mf_soe_fyxorb2f_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:42 o1_mf_soe_fyxosq7c_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:43 o1_mf_soe_fyxov49x_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:44 o1_mf_soe_fyxowklr_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:44 o1_mf_soe_fyxoxyl8_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:45 o1_mf_soe_fyxozcq9_.dbf
-rw-rw----. 1 oracle oracle 5368717312 Nov 16 09:46 o1_mf_soe_fyxp0rwd_.dbf
-rw-rw----. 1 oracle oracle  692068352 Nov 16 09:47 o1_mf_sysaux_fyxp3gc4_.dbf
-rw-rw----. 1 oracle oracle  859840512 Nov 16 09:46 o1_mf_system_fyxp2z72_.dbf
-rw-rw----. 1 oracle oracle 3187679232 Nov 16 09:46 o1_mf_undotbs1_fyxp2666_.dbf

Backup Method	Backup Size
Image Copy	62 GB
No Compression	40 GB
Basic Compression	11 GB
Medium Compression	14 GB
High Compression	95 GB

My next Blog will cover taking this data set and compressing it.