Thursday, December 12, 2013

Monitoring your Exadata health

One of the biggest topics I talk to customers about is the monitoring of your exadata health. 

The best tool for this is the Exachk (see MOS Doc ID 1070954.1)

This document contains the current Exachk release, and any new beta release that is available.

The recommendation for Exachk is to

1) Run the exachk (at a minimum) quarterly, and after any changes are made to the configuration
2) ALWAYS run the current exachk.  This script is periodically updated/improved upon so it is very important to be current
3) Keep track of any failures to ensure that you can identify any new items that appear in the report
4) A score of 80 or above is a good score for production. It is very rare to have a score that is 99+.

There are also a great whitepaper  released in Sept. 2013 (just a few months ago).

This white paper can be  here.

http://www.oracle.com/technetwork/database/availability/exadata-health-resource-usage-2021227.pdf

Wednesday, December 11, 2013

X4-2 Exadata Announcement

These the differences with the new X4-2 just announced, along with a table comparing the differences.
1) Double the size of flashcache
2) Switch from 3tb drives to 4tb drives (HC)
3) More cpu cores
4) Increase in Infiniband throughput by using an Active-Active configuration
5) Automatic Flash compression on X3 and X4 systems (using the ACO option)


x2 X3 X4
Database
Processesor 2 x Six-Core Intel Xeon® X5675 Processors (3.06 GHz) 2 x Eight-Core Intel Xeon®E5-2690 Processors (2.9 GHz) 2 X Twelve-Core Intel® Xeon® E5-2697 V2 Processors (2.7 GHz)
Memory 96G 128g/256g 256g
Disk controller
Disk Controller HBA with 512MB Batter Backed Write Cache
Disk Controller HBA with 512MB Batter Backed Write Cache Disk Controller HBA with 512MB Batter Backed Write Cache
Internal disks 4 x 300 GB 10,000 RPM SAS Disks 4 x 300 GB 10,000 RPM Disks 4 x 600 GB 10,000 RPM Disks
Infiniband 2 x QDR (40Gb/s) Ports 2 x QDR (40Gb/s) Ports 2 x QDR (40Gb/s) Ports
Ethernet 2 x 10 Gb Ethernet Ports based on the Intel 82599 10GbE Controller  4 x 1/10 Gb Ethernet Ports (copper) 4 x 1/10 Gb Ethernet Ports (copper)
Ethernet 4 x 1 Gb Ethernet Ports 2 x 10 Gb Ethernet Ports (optical) 2 x 10 Gb Ethernet Ports (optical)
Full Rack 96 CPU cores and 768 gb memory for database processing (12 CPU cores and 96 GB memory per Database Server)  128 CPU cores and 1TB or  2 TB memory for database processing (16 CPU cores and 256 GB memory per Database Server)  192 CPU cores and 2TB memory for database processing (24 CPU cores and up to 512 GB memory per Database Server)
Storage Cells
CPU
2 x Six-Core Intel® Xeon® L5640 (2.26 GHz) Processors
2 x Six-Core Intel® Xeon® E5-2630L (2.0 GHz processors) 2 x Six-Core Intel® Xeon® E5-2630 v2 (2.6 GHz processors)
Memory 24 GB 64 GB 96 GB
HC (High Capacity)
Disk Bandwidth¹
Up to 18 GB/second of uncompressed disk bandwidth
Up to 18 GB/second of uncompressed disk bandwidth
Up to 20 GB/second of uncompressed disk bandwidth
Flash Bandwidth¹ Up to 68 GB/second of uncompressed Flash data bandwidth Up to 93 GB/second of uncompressed Flash data bandwidth Up to 100 GB/second of uncompressed Flash data bandwidth
Disk IOPS ² Up to 28,000 Database Disk IOPS Up to 28,000 Database Disk IOPS Up to 32,000 Database Disk IOPS
Flash read IOPS ² Up to 1,500,000 Database Flash IOPS Up to 1,500,000 Database Flash IOPS Up to 2,660,000 Database Flash IOPS
Flash write IOPS³ N/A Up to 1,000,000 Database Flash IOPS Up to 1,680,000 Database Flash IOPS
Flash Data Capacity (raw) 5.3 TB Exadata Smart Flash Cache 22.4 TB 44.8 TB
Disk Data capacity (raw) 504 TB of raw disk data capacity 504 TB 672 TB
Disk Data capacity (Usable)
Up to 224 TB of uncompressed usable capacity
224 TB 300 TB
HP (High Performance)
Disk Bandwidth¹
Up to 25 GB/second of uncompressed disk bandwidth
Up to 25 GB/second of uncompressed disk bandwidth
Up to 24 GB/second of uncompressed disk bandwidth
Flash Bandwidth¹ Up to 75 GB/second of uncompressed Flash data bandwidth Up to 100 GB/second of uncompressed Flash data bandwidth Up to 100 GB/second of uncompressed Flash data bandwidth
Disk IOPS ² Up to 50,000 Database Disk IOPS Up to 50,000 Database Disk IOPS Up to 50,000 Database Disk IOPS
Flash read IOPS ² Up to 1,500,000 Database Flash IOPS Up to 1,500,000 Database Flash IOPS Up to 2,660,000 Database Flash IOPS
Flash write IOPS³ N/A Up to 1,000,000 Database Flash IOPS Up to 1,680,000 Database Flash IOPS
Flash Data Capacity (raw) 5.3 TB Exadata Smart Flash Cache 22.4 TB 44.8 TB
Disk Data capacity (raw) 100 TB of raw disk data capacity 100 TB 200 TB
Disk Data capacity (Usable)
Up to 45 TB of uncompressed usable capacity
45 TB 90 TB
¹Bandwidth is peak physical scan bandwidth achieved running SQL, assuming no database compression. Effective user data bandwidth is higher when database compression is used.
 ²Based on 8K IO requests running SQL. Note that the IO size greatly affects Flash IOPS. Others quote IOPS based on 2K or smaller IOs and are not relevant for databases.
³Based on 8K IO requests running SQL. Flash write I/Os measured at the storage servers after ASM mirroring. Database writes will usually issue multiple storage IOs to maintain redundancy.
⁴Raw capacity is measured in standard disk drive terminology with 1 GB = 1 billion bytes. Capacity is measured using normal powers of 2 space terminology with 1 TB = 1024 * 1024 * 1024 * 1024 bytes. Actual formatted capacity is less.
⁵Raw capacity is measured in standard disk drive terminology with 1 GB = 1 billion bytes. Capacity is measured using normal powers of 2 space terminology with 1 TB = 1024 * 1024 * 1024 * 1024 bytes. Actual formatted capacity is less.
⁶Actual space available for a database after mirroring (ASM normal redundancy) while also providing adequate space (one disk on Quarter and Half Racks and two disks on a Full Rack) to reestablish the mirroring protection after a disk failure in the normal redundancy case.

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Tuesday, November 12, 2013

Oracle 12c PL/SQL improvements.


Last week I was giving a presentation for the UNYOUG (Upstate NY Oracle users Group) and I talked about the new features in 12c (along with In-Memory database).

I thought I would share some thoughts after the meeting.

I went through Tom Kyte's top 12 new features, and surprisingly the top feature that excited people was the PL/SQL improvements. 

The PL/SQL improvements had to do with the ability to write a PL/SQL as part of the query.

Lets say currently with 11g you have a function that includes the days between 2 dates.

  CREATE OR REPLACE FUNCTION Days_Between 
             (first_dt DATE, second_dt DATE)
                RETURN NUMBER IS 
       dt_one NUMBER
       dt_two NUMBER
BEGIN 
      dt_one := TO_NUMBER(TO_CHAR(first_dt, 'DDD')); 
      dt_two := TO_NUMBER(TO_CHAR(second_dt, 'DDD'));  
           RETURN (dt_two - dt_one); 
 END Days_Between;   

select Days_between(start_date,end_date) from mytable;



The problem is that in order to test this function you need to create the function.  There are multiple issues that developers face with having to do this.
  1. Developers often don't have the authority to create/change functions, especially if they need to be owned by a different schema
  2. Replacing the current function affects other users and this may not be desirable while debugging changes.
  3. Testing against production data is often not possible because of authorization, and collision issues.

The answer in 12c is the ability to include a function in the "WITH" clause.. The above would become


WITH  FUNCTION Days_Between
             (first_dt DATE, second_dt DATE)
                RETURN NUMBER IS
       dt_one NUMBER;
       dt_two NUMBER;
BEGIN
      dt_one := TO_NUMBER(TO_CHAR(first_dt, 'DDD'));
      dt_two := TO_NUMBER(TO_CHAR(second_dt, 'DDD'));
           RETURN (dt_two - dt_one);
 END Days_Between;  
select Days_between(start_date,end_date) from mytable;

So. what about Procedures you ask ? You can also include procedures in the mix.  The main purpose of doing this is to include any procedures that are invoked from the function.  This way you can include all the "dependencies" in the with clause. 

Finally, I read an article talking about how much this improves performance too.

http://www.oracle-base.com/articles/12c/with-clause-enhancements-12cr1.php#plsql-support

but to the developers I talked to the big advantage was with the ability to test..

As far as performance gains, I don't know how much I would put reusable code (like functions) directly into a sql statement. It would be a bear to support any changes to a "common function" defined multiple places.
 

 

Wednesday, January 9, 2013

Performance and Indexes with oracle

It's been a while since I've written a post, but twice this week, the same issue came up..

The story goes like this.. "I have a query that is using indexes not FTS, but it is much slower then expected".  It seems most folks have it drummed into their heads that Indexes are fastest.

This is the statement I've made twice....

"The only thing worse than a FTS is an index lookup of the whole table."  I figured I would show you what I mean.

First I create 2 tables..

TEST_TABLE with 76,989 rows of data.  There is a primary key.
DRIVER  with the same rows of test_table.

This is the 2 test I did.

1) I created DRIVER with 1 row, and analyzed it , then I deleted the row, and inserted all the rows from TEST_TABLE.
2) I ran the following query which should return every row.

select  /*+ GATHER_PLAN_STATISTICS */  count(distinct a.capture_time)
from test_table a,
     driver b
where a.pval=b.pval
and b.instance_number < 20;

So what happens ?  since the statistics on DRIVER say there is only row you can see the plan and actual vs estimated below.







----------------------------------------------------------------------------------------------        
| Id  | Operation                       | Name       | Starts | E-Rows | A-Rows |   A-Time   |    
----------------------------------------------------------------------------------------------   

PLAN_TABLE_OUTPUT                                                                                                                           
----------------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT                |            |      1 |        |      1 |00:00:00.86 |
|   1 |  SORT AGGREGATE                 |            |      1 |      1 |      1 |00:00:00.86 |
|   2 |   VIEW                          | VW_DAG_0   |      1 |      1 |  77961 |00:00:01.28 |
|   3 |    HASH GROUP BY                |            |      1 |      1 |  77961 |00:00:01.01 |
|   4 |     NESTED LOOPS                |            |      1 |        |  77989 |00:00:01.00 |
|   5 |      NESTED LOOPS               |            |      1 |      1 |  77989 |00:00:00.58 |
|*  6 |       TABLE ACCESS FULL         | DRIVER     |      1 |      1 |  77989 |00:00:00.07 |
|*  7 |       INDEX UNIQUE SCAN         | PVAL_KEY   |  77989 |      1 |  77989 |00:00:00.21 |
|   8 |      TABLE ACCESS BY INDEX ROWID| TEST_TABLE |  77989 |      1 |  77989 |00:00:00.22 |
----------------------------------------------------------------------------------------------
                                                                                                

Since the Optimizer is only expecting 1 row to come back from the table DRIVER, it does an index lookup on TEST_TABLE, for every row. Notice the actual number of rows is the full table.

Now lets look at the cost of this index lookup.


select  /*+ GATHER_PLAN_STATISTICS */  count(distinct a.capture_time)
from test_table a,
     driver b
where a.pval=b.pval
and b.instance_number < 20

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        2      0.84       0.85          0      83932          0           1
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        4      0.84       0.85          0      83932          0           1


OK.  so the cost of the index lookup row-by-row is .85 seconds elapsed time.

Now after analyzing the DRIVER table, you can see the plan changed to a FTS.


------------------------------------------------------------------------------------
| Id  | Operation             | Name       | Starts | E-Rows | A-Rows |   A-Time   |
------------------------------------------------------------------------------------
PLAN_TABLE_OUTPUT                                                                                                                           
------------------------------------------------------------------------------------
|   0 | SELECT STATEMENT      |            |      1 |        |      1 |00:00:00.16 |
|   1 |  SORT AGGREGATE       |            |      1 |      1 |      1 |00:00:00.16 |
|   2 |   VIEW                | VW_DAG_0   |      1 |  76723 |  77961 |00:00:00.40 |
|   3 |    HASH GROUP BY      |            |      1 |  76723 |  77961 |00:00:00.23 |
|*  4 |     HASH JOIN         |            |      1 |  76723 |  77989 |00:00:01.23 | 
|*  5 |      TABLE ACCESS FULL| DRIVER     |      1 |  76723 |  77989 |00:00:00.22 |
|   6 |      TABLE ACCESS FULL| TEST_TABLE |      1 |  79110 |  77989 |00:00:00.22 |
------------------------------------------------------------------------------------
                                                                                              


Notice the actual rows, and estimates match.  You can also see it is a FTS.

Now for the run time stats with the FTS.

select  /*+ GATHER_PLAN_STATISTICS */  count(distinct a.capture_time)
from test_table a,
     driver b
where a.pval=b.pval
and b.instance_number < 20

call     count       cpu    elapsed       disk      query    current        rows
------- ------  -------- ---------- ---------- ---------- ----------  ----------
Parse        1      0.00       0.00          0          0          0           0
Execute      1      0.00       0.00          0          0          0           0
Fetch        2      0.15       0.15          0       1390          0           1
------- ------  -------- ---------- ---------- ---------- ----------  ----------
total        4      0.15       0.15          0       1390          0           1

     

WOW.. look at that the FTS took .15 seconds compared to .85 seconds.

The bottom line is.. The next time you talk to developers, and they think their query should be fast because they are using an index, look deeper.  The biggest clue is to look at the Estimate vs Actual for the plan.  The index might not be what you want. FTS's can be good.