CBO and Update Statistics

Hi ,
Ver. 10204
The cbo usually working very well when it have an update statistics ,
Orcale also recommand to manually gather statistics after bulk loading.
Could one show simple TEST CASE where oracle is choosing a poor execution plan due to non update statistics?
Thanks

user546852 wrote:
The cbo usually working very well when it have an update statistics ,
Orcale also recommand to manually gather statistics after bulk loading.
Could one show simple TEST CASE where oracle is choosing a poor execution plan due to non update statistics?I've written a blog note some time ago which explains potential issues regarding SQL statement tuning. The sample used there is based on incorrect object statistics.
Regards,
Randolf
Oracle related stuff blog:
http://oracle-randolf.blogspot.com/
SQLTools++ for Oracle (Open source Oracle GUI for Windows):
http://www.sqltools-plusplus.org:7676/
http://sourceforge.net/projects/sqlt-pp/

Similar Messages

Reindexing and Update Statistics on Standby Server

In an environment where we have enabled Always On, we have configured a Maintenance Plan that constitutes on the following sub plans: a. Reindexing b. UpdateStatistics and c. Integrity Checks. However, for the databases that are getting synchronized on
the Standby Server (they are on "Synchronizing" mode), can we also configure the same Maintenance plan in the standby server. Will there be a problem in running these jobs on the databases that are in "Synchronizing" mode?

The standby/replicas databases are either in read-only or constant recovery mode and, therefore, no data modification can be performed. This includes running maintenance jobs such as reindexing and updating of statistics. The better approach here is to
use a custom maintenance script, such as that from
Ola Hallengren, that only reindex those that are necessary to minimize the amount of transaction log records generated on the primary and keep the standby in synchronized state.
Edwin Sarmiento SQL Server MVP | Microsoft Certified Master
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IF Auto Update Statistics ENABLED in Database Design, Why we need to Update Statistics as a maintenance plan

Hi Experts,
IF Auto Update Statistics ENABLED in Database Design, Why we need to Update Statistics as a maintenance plan for Daily/weekly??
Vinai Kumar Gandla

Hi Vikki,
Many systems rely solely on SQL Server to update statistics automatically(AUTO UPDATE STATISTICS enabled), however, based on my research, large tables, tables with uneven data distributions, tables with ever-increasing keys and tables that have significant
changes in distribution often require manual statistics updates as the following explanation.
1.If a table is very big, then waiting for 20% of rows to change before SQL Server automatically updates the statistics could mean that millions of rows are modified, added or removed before it happens. Depending on the workload patterns and the data,
this could mean the optimizer is choosing a substandard execution plans long before SQL Server reaches the threshold where it invalidates statistics for a table and starts to update them automatically. In such cases, you might consider updating statistics
manually for those tables on a defined schedule (while leaving AUTO UPDATE STATISTICS enabled so that SQL Server continues to maintain statistics for other tables).
2.In cases where you know data distribution in a column is "skewed", it may be necessary to update statistics manually with a full sample, or create a set of filtered statistics in order to generate query plans of good quality. Remember,
however, that sampling with FULLSCAN can be costly for larger tables, and must be done so as not to affect production performance.
3.It is quite common to see an ascending key, such as an IDENTITY or date/time data types, used as the leading column in an index. In such cases, the statistic for the key rarely matches the actual data, unless we update the Statistic manually after
every insert.
So in the case above, we could perform manual statistics updates by
creating a maintenance plan that will run the UPDATE STATISTICS command, and update statistics on a regular schedule. For more information about the process, please refer to the article:
https://www.simple-talk.com/sql/performance/managing-sql-server-statistics/
Regards,
Michelle Li

Is reindexing and rebuilding statistics nessiary

I'm reducing the size of a SQL database from 115905 records to about 110000 records. My SQL server administrator is nowhere to be found. Is it critical to have the database rebuild
indexes and update statistics before I let users get back into the front end application and do regular work?
I've been doing these archives daily for a week and he rebuilds indexes and updates statistics each day before I let the users get in.

Since you deleted large no of records updatiing stats would be a good option .And if you rebuild index with full scan,which i dont think would be necessary to do after delete process,stats would automatically be updated .
More or less index rebuild depends on fragmentation >30 % you rebuild and between 30 and 10 you reorganize.
Since it is your daily task I would suggest you to look at Ola hallengren script
http://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html
Please mark this reply as the answer or vote as helpful, as appropriate, to make it useful for other readers

Check and Update Optimizer Statistics Error

Hello,
I have scheduled 'Check and Update Optimizer Statistics' from DB 13 but I always get this error.
BR0280I BRCONNECT time stamp: 2009-01-05 01.00.46
BR0301E SQL error -20000 at location stats_ind_collect-3, SQL statement:
'BEGIN DBMS_STATS.GATHER_INDEX_STATS (OWNNAME => '"SAPSR3"', INDNAME => '"/BIC /B0000412000KE"', ESTIMATE_PERCENT => 30, DEGREE => NULL, NO_INVALIDATE => FALSE); END;'
ORA-20000: index "SAPSR3"."/BIC/B0000412000KE" or partition of such index is in unusable state
ORA-06512: at "SYS.DBMS_STATS", line 10610
ORA-06512: at "SYS.DBMS_STATS", line 10645
ORA-06512: at line 1
BR0886E Checking/collecting statistics failed for index SAPSR3./BIC/B0000412000KE
Tried checking the table /BIC/B0000412000KE and got this from the check:
Enhancement category for table missing
Enhancement category for include or subtype missing
Table /BIC/B0000412000 was checked with warnings
I am still checking what this means but appreciate you have any idea on how to solve it.
Thank you.
Best Regards,
Julius
Edited by: Julius Baron Manuel on Jan 7, 2009 7:39 AM

Hi Julius,
Have your tried scheduling the update stats via DB13 'Immediately'. ??? Does it still gives you the same error when its done 'immediately'?
Try out DB02 and check your whole Database along with missing indexes. Refresh database and update histories.
Regards,
Pranay

Check and update optimizer statistics failed

Hellow Friends,
After running job Check and update optimizer statistics each and every time from db13 in my BI production server it got failed please
view the logs
BR0301E SQL error -20000 at location stats_tab_collect-20, SQL statement:
'BEGIN DBMS_STATS.GATHER_TABLE_STATS (OWNNAME => '"SAPSR3"', TABNAME => '"/BIC/B0000228000"', ESTIMATE_PERCENT => NULL, METHOD_OPT => 'FOR ALL
ORA-20000: index "SAPSR3"."/BIC/B0000228000KE" or partition of such index is in unusable state
ORA-06512: at "SYS.DBMS_STATS", line 13159
ORA-06512: at "SYS.DBMS_STATS", line 13179
ORA-06512: at line 1
BR0886E Checking/collecting statistics failed for table SAPSR3./BIC/B0000228000
BR0280I BRCONNECT time stamp: 2009-05-19 18.17.19
BR0883I Table selected to collect statistics after check: SAPSR3./BIC/B0000229000 (161130/1480:0:0)
BR0280I BRCONNECT time stamp: 2009-05-19 18.17.19
BR0881I Collecting statistics for table SAPSR3./BIC/B0000229000 with method/sample E/P10 ...
BR0280I BRCONNECT time stamp: 2009-05-19 18.17.21
BR0301E SQL error -20000 at location stats_tab_collect-20, SQL statement:
'BEGIN DBMS_STATS.GATHER_TABLE_STATS (OWNNAME => '"SAPSR3"', TABNAME => '"/BIC/B0000229000"', ESTIMATE_PERCENT => 10, METHOD_OPT => 'FOR ALL C
ORA-20000: index "SAPSR3"."/BIC/B0000229000KE" or partition of such index is in unusable state
ORA-06512: at "SYS.DBMS_STATS", line 13159
ORA-06512: at "SYS.DBMS_STATS", line 13179
ORA-06512: at line 1
BR0886E Checking/collecting statistics failed for table SAPSR3./BIC/B0000229000
BR0280I BRCONNECT time stamp: 2009-05-19 18.17.21
BR0883I Table selected to collect statistics after check: SAPSR3./BIC/B0000230000 (0/13545:0:0)
BR0280I BRCONNECT time stamp: 2009-05-19 18.17.21
BR0881I Collecting statistics for table SAPSR3./BIC/B0000230000 with method/sample E/P30 ...
BR0280I BRCONNECT time stamp: 2009-05-19 18.17.21
BR0301E SQL error -20000 at location stats_tab_collect-20, SQL statement:
'BEGIN DBMS_STATS.GATHER_TABLE_STATS (OWNNAME => '"SAPSR3"', TABNAME => '"/BIC/B0000230000"', ESTIMATE_PERCENT => 30, METHOD_OPT => 'FOR ALL C
ORA-20000: index "SAPSR3"."/BIC/B0000230000KE" or partition of such index is in unusable state
ORA-06512: at "SYS.DBMS_STATS", line 13159
ORA-06512: at "SYS.DBMS_STATS", line 13179
ORA-06512: at line 1
BR0886E Checking/collecting statistics failed for table SAPSR3./BIC/B0000230000
Please help me to resolve the issue.

some of your PSA tables are inconsistent - ex: /BIC/B0000228000 - check PSA partitioning in RSRV to correct the same or delete data from the same using SE14 and try running the same.

PSAP SID TABLESPACE UPDATE STATISTICS ADVANTAGES AND DISADVANTAGES

Dear All,
Can anyone explain me if we select PSAP SID table space only for update statistics from DB13 Instead of selecting all tables for update statistics,what are the advantages and disadvantages of selecting only PSAP SID tablespace .
I will be glad if you can suggest any related sapnote or sapmaterial.
we are working on SAP ECC5 and oracle version id 9i and operating system is windows.

Hi arunkumar ,
When you are updating statitics then update for all table space why for one only.After all it will increase the performance of your database.
Regards
Ashok

UPDATE STATISTICS and merry-go-round scanning

Hello everybody,
if I do UPDATE STATISTICS [table] SQL Server internally scans the table multiple times for different statistics objects (good description by Kendra Little at
http://www.brentozar.com/archive/2014/01/update-statistics-the-secret-io-explosion/).
Does anybody know whether these scans are executed parallel to each other and can profit from merry-go-round scan mechanism? (http://msdn.microsoft.com/en-us/library/ms191475.aspx).
Thanks in advance.

My impression is that they executed one by one on the same thread, but I have not researched this very closely.
Erland Sommarskog, SQL Server MVP, [email protected]

Update Statistics and Rebuild of Indexes

Hi friends,
If I execute the Update statistics for a given table thru DB20 does it have any effect on the indexes of this table or is it necessary to rebuild the index using db02
Regards
Aliila

Updating Statistics does not rebuild index while in update states logs it will show you information regarding which indexes needs to be rebuiled which you can rebuild by brtools or executing rsanaora prg in se38.
Shivam

Updating statistics after insert

Is it possible, without creating a custom post-map process, to update statistics after inserting rows into a table. I've tried setting different parameters within OWB to no avail.
Please respond only if you have actually succeeded in updating statistics without writing code. I've already read the docs and experimented.
Thanks.
Garrett

Hi,
why do you think so? The analyze configuration
results in a procedure which calls
WB_RT_MAPAUDIT_UTIL_INVOKER for each target table
which then calls the DBMS_STATS-Package? What is
misssing for the CBO? I'm a little bit confused?!
Regards,
DetlefThanks for the info. I'm a little confused. I thought that I had the analyze table box checked in the configuration and statistics were not updated. However, when I looked again, it was not checked. My error. Ran another test and statistics were updated. Sorry for the confusion.
G.

Update statistics with 640_EX2 kernel

Hello,
I'm no longer able to do UPD_CHECK, UPD_COND and UPD_UNCOND since upgrading to a 640_EX2 kernel.
This happens on WebAS 6.20 on Linux IA32 and on WebAS 6.40 on Linux X86_64. Scheduling backups and verifys still works from db13. MaxDB version is 7.6.4.07. The problem exists with versions 120 and 212 of dbadaslib.so.
Are these commands working for anyone? I suspect this could be one of these nice C++ ABI incompatibility problems, because libSQLDBC76.so is linked against libstdc+.so.5 and dbadaslib.so is linked against libstdc.so.5 and libstdc+.so.6.
Since I am on an unsupported Linux distro I would like to know whether this happens on supported distros, too.
Thank you,
Sebastian

Thank you for pointing me to the logs again, I scanned them too superficially last time.
This is written to the trace file of a batch process:
C Starting Update Statistics on connection 2 ...
C *** ERROR => connection for UPDSTAT is not available
[dbupdsdb.cpp 140]
This is interesting, because the connection test in db59 is successful for all 4 types of connections.

SQL 2008 R2 Best Practices for Updating Statistics for a 1.5 TB VLDB

We currently have a ~1.5 TB VLDB (SQL 2008 R2) that services both OLTP and DSS workloads pretty much on a 24x7x365 basis. For many years we have been updating statistics (full scan- 100% sample size) for this VLDB once a week on the weekend, which
is currently taking up to 30 hours to complete.
Somewhat recently we have been experiencing intermitent issues while statistics are being updated, which I doubt is just a coincidence. I'd like to understand exactly why the process of updating statistics can cause these issues (timeouts/errors). My theory
is that the optimizer is forced to choose an inferior execution plan while the needed statistics are in "limbo" (stuck between the "old" and the "new"), but that is again just a theory. I'm somewhat surprised that the "old" statistics couldn't continue to
get used while the new/current statistics are being generated (like the process for rebuilding indexes online), but I don't know all the facts behind this mechanism yet so that may not even apply here.
I understand that we have the option of reducing the sample percentage/size for updating statistics, which is currently set at 100% (full scan). Reducing the sample percentage/size for updating statistics will reduce the total processing time, but
it's also my understanding that doing so will leave the optimizer with less than optimal statistics for choosing the best execution plans. This seems to be a classic case of not being able to have one’s cake and eat it too.
So in a nutshell I'm looking to fully understand why the process of updating statistics can cause access issues and I'm also looking for best practices in general for updating statistics of such a VLDB. Thanks in advance.
Bill Thacker

I'm with you. Yikes is exactly right with regard to suspending all index optimizations for so long. I'll probably start a separate forum thread about that in the near future, but for now lets stick to the best practices for updating statistics.
I'm a little disappointed that multiple people haven't already chimed in about this and offered up some viable solutions. Like I said previously, I can't be the first person in need of such a thing. This database has 552 tables with a whole lot more statistics
objects than that associated with those tables. The metadata has to be there for determining which statistics objects can go (not utilized much if at all so delete them- also produce an actual script to delete the useless ones identified) and what
the proper sample percentage/size should be for updating the remaining, utilized statistics (again, also produce a script that can be used for executing the appropriate update statistics commands for each table based on cardinality).
The above solution would be much more ideal IMO than just issuing a single update statistics command that samples the same percentage/size for every table (e.g. 10%). That's what we're doing today at 100% (full scan).
Come on SQL Server Community. Show me some love :)
Bill Thacker

PeopleSoft Database Update Statistics

I am trying to find out what is the best practices for implementing the Update statistics on Psoft Database. Any help or documentation regarding will be a great help
I am looking for
what is the best practice for update statistics on oracle , Intervals , Tables , do we need to include any custom script to generate and include all big tables.

I was the one who designed the pscbo_stats package to leverage the statistics collection techniques used in EBS and Seibel. (Mr. Sierra was the wizard who coded it.) I just noticed this thread and wanted to comment.
If you are using the pscbo_stats, the gather_schema_stats() procedure will by default gather only stale statistics, so it can be run regularly. I suggest weekly. You can follow the contents of the pscbo_log table for historical data for all (non-dynamic) stats gathering activities.
If you find there is a table that constantly stale and forcing you to think that the schema statistics should gathered more often, you may want to have two schedules - one weekly for schema, and one more often (daily?) to capture the more volatile objects excepting, of course, those that are already dynamically sampled.
There may be objects that are volatile enough that they should be added to the Stage Table Exception table. (see the stage_table_ins() procedure) We added that feature to configure dynamic sampling to work on volatile table - tables that are not working storage for COBOL and App Engine but are so often stale that they should be dynamically sampled.
I find that there are a few transactional tables that work well when dynamically sampled. For example, PSTREESELECT* tables can be problematic if they are dynamically rebuilt by a nVision report book - the end points can get stale quickly. They may be a good candidate for dynamic sampling.
Lastly, I am very interested to know user experience with the pscbo_stats package. Please post your comments to the communities.oracle.com forum for "Install/Upgrade PSFT".

Update statistics error in prod

Dear Experts ,
we are facing an error while updating statistics by using db13
please check on log below
18.05.2011     18:52:41     Job started
18.05.2011     18:52:41     Step 001 started (program RSDBAJOB, variant &0000000000047, user ID BASIS)
18.05.2011     18:52:42     No application server found on database host - rsh/gateway will be used
18.05.2011     18:52:42     Execute logical command BRCONNECT On host PRDHOSR
18.05.2011     18:52:42     Parameters: -u / -jid STATS20110518185240 -c -f stats -t ALL
18.05.2011     18:53:34     BR0801I BRCONNECT 7.00 (40)
18.05.2011     18:53:34     BR1304W Checking SAP license failed at location BrLicCheck-108
18.05.2011     18:53:34     BR0602W No valid SAP license found - please contact SAP
18.05.2011     18:53:34     BR0805I Start of BRCONNECT processing: cefxifuy.sta 2011-05-18 18.52.44
18.05.2011     18:53:34     BR0484I BRCONNECT log file: /oracle/PRD/sapcheck/cefxifuy.sta
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.52.53
18.05.2011     18:53:34     BR0813I Schema owners found in database PRD: SAPSR3*, SAPSR3DB%
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.05
18.05.2011     18:53:34     BR0814I Number of tables/partitions in schema of owner SAPSR3: 32818/10
18.05.2011     18:53:34     BR0836I Number of info cube tables found for owner SAPSR3: 143
18.05.2011     18:53:34     BR0814I Number of tables in schema of owner SAPSR3DB: 722
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.24
18.05.2011     18:53:34     BR0815I Number of indexes/partitions in schema ofowner SAPSR3: 43208/13
18.05.2011     18:53:34     BR0815I Number of indexes in schema of owner SAPSR3DB: 1051
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.29
18.05.2011     18:53:34     BR0818I Number of tables found in DBSTATC for owner SAPSR3: 814
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.29
18.05.2011     18:53:34     BR0807I Name of database instance: PRD
18.05.2011     18:53:34     BR0808I BRCONNECT action ID: cefxifuy
18.05.2011     18:53:34     BR0809I BRCONNECT function ID: sta
18.05.2011     18:53:34     BR0810I BRCONNECT function: stats
18.05.2011     18:53:34     BR0812I Database objects for processing: ALL
18.05.2011     18:53:34     BR0851I Number of tables with missing statistics:0
18.05.2011     18:53:34     BR0852I Number of tables to delete statistics: 0
18.05.2011     18:53:34     BR0854I Number of tables to collect statistics without checking: 0
18.05.2011     18:53:34     BR0855I Number of indexes with missing statistics: 0
18.05.2011     18:53:34     BR0856I Number of indexes to delete statistics: 0
18.05.2011     18:53:34     BR0857I Number of indexes to collect statistics: 0
18.05.2011     18:53:34     BR0853I Number of tables to check (and collect ifneeded) statistics: 33537
18.05.2011     18:53:34     BR0126I Unattended mode active - no operator confirmation required
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.31
18.05.2011     18:53:34     BR0817I Number of monitored/modified tables in schema of owner SAPSR3: 32818/1055
18.05.2011     18:53:34     BR0817I Number of monitored/modified tables in schema of owner SAPSR3DB: 722/8
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.33
18.05.2011     18:53:34     BR0301E SQL error -2132 at location thr_db_connect-3, SQL statement:
18.05.2011     18:53:34     'ENABLE THREADS'
18.05.2011     18:53:34     SQL-02132: Message 2132 not found; No message file for product=precomp, facility
18.05.2011     18:53:34     BR0310E Connect to database instance PRD failed
18.05.2011     18:53:34
18.05.2011     18:53:34     BR0806I End of BRCONNECT processing: cefxifuy.sta2011-05-18 18.53.33
18.05.2011     18:53:34     BR0280I BRCONNECT time stamp: 2011-05-18 18.53.34
18.05.2011     18:53:34     BR0804I BRCONNECT terminated with errors
18.05.2011     18:53:34     External program terminated with exit code 5
18.05.2011     18:53:34     BRCONNECT returned error status E
18.05.2011     18:53:34     Job finished
please help to solve this error in production
Regards

Dear Experts ,
now i got an error
because of oracle client update statistics are failed now i required to upgrade oracle client
please share your valiable knoledge how can i upgrade my oracle client 10.2.0.2 to 10.2.0.4, i checked note 819829 now i need your suggesitions on this activity
and also pre - requsits to upgrade (steps)
Regards

DB13 CheckDb and Update Stats Error

Hi,
I am getting below error in CheckDb and Update stats:
Update Stats:
BR0301E SQL error -20003 at location stats_tab_collect-20, SQL statement:
'BEGIN DBMS_STATS.GATHER_TABLE_STATS (OWNNAME => '"SAPCRM"', TABNAME => '"WSSOAPPROP_DARK"', ESTIMATE_PERCENT => NULL, METHOD_OPT => 'FOR ALL COLUMNS SIZE 1', DEGREE => NULL
ORA-20003: Specified bug number (5099019) does not exist
ORA-06512: at "SYS.DBMS_STATS", line 14537
ORA-06512: at "SYS.DBMS_STATS", line 14558
ORA-06512: at line 1
Check Db :
BR0301E SQL error -1031 at location BrDbdiffRead-1, SQL statement:
'PREPARE stmt_5 STATEMENT FROM'
'SELECT OBJNAME FROM "SAPSR3".DBDIFF WHERE DBSYS IN ('ORACLE', ' ') AND OBJTYPE = 'TABL' AND DIFFKIND IN ('02', '61', '99') ORDER BY OBJNAME'
ORA-01031: insufficient privileges
BR0806I End of BRCONNECT processing: ceeuoqja.chk 2010-12-17 06.30.46
BR0280I BRCONNECT time stamp: 2010-12-17 06.30.46
BR0804I BRCONNECT terminated with errors
Above both errors are of different System and both system are just get ready after System Copy of PRD Server.
Please suggest possible route cause of this error.
Shivam

for update stats issue check Note 1417124 - Error ORA-20001 in statistics class CL_SDB_ORA_UPDATE_STATS
for DB check error go through note 400241
Please search before you post your thread on SDN

CBO and Update Statistics

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