Why DBCS (Oracle Base Database Service) in OCI can make a DBA's life much easier (even with BYOL)

DBCS (now named Oracle Base Database service, but I will call it DBCS throughout this post) in OCI  can help make a DBA's life easier.  When I was testing the new Autonomous Recovery Service for Oracle Database in OCI, I created a LOT of different DBCS systems to test backup and recovery.  Along the way I learned a lot about the workings of DBCS, and I came to appreciate how it makes sense, even if you are a BYOL (bring your own license) customer.

I'm more of a an "old school" DBA, preferring command line, and scripting processes myself.  I am typically not a fan of automation.  When using DBCS I was surprised by all the things it would do for me that I would have to do manually.

Install oracle software and create a database

Having installed oracle software hundreds of times, and having created test databases, I didn't think I would care much about automation that did this for me.

Central Software image management

What I found in OCI, is that you can create your own software images that can be used to ensure each new database environment is consistent.  OCI gives you ability to create your own set of release images (which can include patches).  This ensures each time I create a new DBCS environment, and choose my custom image, it's running the same version in all environments. No more installing base release, then patches, and then then any possible one-off patches.  This makes the installation of the database software much, much easier, and ensures consistency.

Easy Database creation

Recently I've gotten familiar with performing a silent database creation, as using dbca isn't always easy to configure.  The tooling provided by DBCS will not only create a database for you, but will also configure TDE encryption (with a local wallet, or using OCI vault).  It can even create a RAC database across 2 nodes.  And don't forget, it can create the standby for me also.

Configure ASM storage

Now this is the most interesting piece I found when using DBCS.  Not only does the DBCS service create a disk group, but it automatically stripes multiple block volumes together maximizing performance.  This is a HUGE help in ensuring I am getting the best performance.

When I was going through what the configuration did, I tried to build tables showing how the different storage sizes translate to the storage configurations.

There were 2 configurations and DB data storage sizes, one for Flex, and one for Standard shapes.

Flex

First I looked at flex, and regardless of the performance level these were the sizes.

Then within Flex, I looked at the "Balanced performance" configuration.

Balanced Performance configuration

You can see that as the DB storage available goes up, the number of disks goes up also allowing for a higher  possible IOPS than you would get from a single Block Storage device.

Below is the chart for "High Performance"

High Performance configuration

You can see that the IOPS is even higher, and it is using even more disks to get that performance.

Standard

Next looked at standard shapes, and regardless of the performance level these were the sizes. Note that with Standard shapes, there were many more options for configurations.

Balanced Performance configuration

High Performance configuration

Benefits of DBCS

I also went through what some of the other benefits of DBCS are, and below is the list I came up with.

• When using the DBCS service,  the storage cost is based on the Block Storage cost. This is the same cost as you would pay in an IaaS service.  Having the storage striped and configured for maximum IOPS makes this a huge plus.

• DBCS allows you purchase licenses if you don't have enough licenses to use the BYOL option.

• The DBCS service price is based on OCPU and is the same regardless of the shape. Memory is included in the OCPU cost.

• DBCS automatically configures RAC if you choose it.

• DBCS provides tooling that automatically configures backups, can apply patches, and rotate encryption keys.

• DBCS allows you to automate the cloning of your database, and automate any restores.

• DBCS includes TDE, and relieves you of having to own the ASO license.  

Conclusion:

DBCS offers a lot more than you realize. Take a deep dive into what it can do for you to save time as DBA and you also might realize that sometimes tooling along with automation has it's benefits.

Oracle Database recovery using Incremental merge, snapshots, OMF and "switch to copy"

I work with backup and recovery of the Oracle Database, and sometimes this means looking at the Incremental Merge backup strategy.  I know this isn't the best backup/recovery strategy, and below are few posts giving you more detail on the topic.

• Chris Craft's blog post - "Using incremental merge"
• Tim Chien's blog post - "Why CDB(snapshots) are NOT backups"

They have some great points, and I typically don't recommend using incremental merge backups.  The incremental merge backup strategy is almost always paired with snapshots to increase the recovery window.

Below is an image of how these are typically paired with snapshots.

One of the biggest draws of using the incremental merge strategy with snapshots, is the ability to perform a "switch to copy" as a recovery strategy.

NOTE: When you perform "switch to copy" the database is now accessing datafiles using the backup copy.  This is not supported on Exadata for any storage other than Oracle ZFS.

If you review the MOS note "Using External Storage with Exadata (Doc ID 2663308.1)" you will find that "Use of non-Oracle storage for database files is not supported."

Given all of that, I got the question "I am using the incremental merge strategy on Oracle an ZFS appliance using snapshots. If I perform a switch-to-copy recovery of one or more datafiles, how do I avoid forcing a new full backup on the next incremental merge backup?".

I thought this was a great question, and I created a test database, and started googlin'.  Below are some of the posts I looked at.

• Oracle 12c and RMAN switch datafile to copy, is it really so easy?
• Oracle docs for "alter database move datafile"

I started  by using the first post and walked through a testing scenario using a DBCS database in OCI.

My database was a 19.8 database using local storage (to make things easier to see the datafiles), and it was using OMF by default.  

The piece that was missing from the first post was the "alter database move datafile 'xxx' to 'xxx' KEEP;

What I found is that it wasn't so easy with my database using OMF for 2 reasons.

1. Using OMF, you don't specify the "to 'xxx'" since OMF will automatically name the destination datafile.
2. Using "KEEP" is ignored when the source file is OMF.  This meant that the original image copy being used by the database is removed when move process completes.  I couldn't catalog the image copy.

Since it took a bit of research to find the best strategy I wanted to share the process that I would recommend when dealing with OMF and non-OMF image copy backups with snapshots.

NON-OMF image copy backups

1. Snap the backup storage just to preserve the starting point. --> optional but recommended
2. Take the tablespaces offline
3. Perform a "switch to copy" of the datafiles --> This will use the incremental merge backup.
4. Recover the datafiles
5. Bring the tablespaces online ---> Application is running using the external image copy
6. Perform an "alter database move datafile 'xxx' to 'xxx' KEEP; --> Using keep will preserve the original copy, but will only work if the image copy is NOT OMF. If the destination is an OMF file, you will not use the "to"
7. Catalog the image copy that was preserved with the "KEEP" ensuring you use the same tag used for the incremental merge. "catalog datafilecopy '+fra/ocm121/datafile/MONSTER.346.919594959' level 0 TAG 'incr_update';"
8. The next incremental merge will pick up with the updated image copy.

OMF image copy backups

1. Snap the backup storage to create a copy for the switch to copy.
2. Unmount the "current" image copy 
3. Mount the snap copy using the same mount point as the "current" image copy.
4. Take the tablespaces offline
5. Perform a "switch to copy" of the datafiles --> This will use the snap copy of the incremental merge backup on external storage.
6. Recover the datafiles
7. Bring the tablespaces online ---> Application is running using external copies.
8. Perform an "alter database move datafile 'xxx' ; --> Since the source is an OMF file you cannot use "KEEP" to preserve the original copy. The original copy will be removed.
9. Once all moves are complete, unmount the snapped copy.
10. Mount the "current" copy. This is as of when you started this process.
11. Catalog the image copy for all datafiles that performed the "switch to copy" ensuring you use the same tag used for the incremental merge "catalog datafilecopy '+fra/ocm121/datafile/MONSTER.346.919594959' level 0 TAG 'incr_update';"
12. You can now destroy the snap that was created to perform the switch to copy.
13. The next incremental merge will pick up with the current image datafile copies where it left off.

As you can see, using OMF greatly complicates preserving the incremental merge backup, and forces you to start at the last backup.