Monday Aug 24, 2015

How to avoid ORA-06512 and ORA-20000 when Concurrent Statistics Gathering is enabled. New in 12.1 Database, Concurrent Statistics Gathering, Simultaneous for Multiple Tables or Partitions

Oracle Database 12.1 introduces a new feature, Concurrent Statistics Gathering. 

Concurrent statistics collection is simply the ability to gather statistics on multiple tables, or table partitions, at the same time.  When CONCURRENT statistics gathering is enabled, you can execute each statistics gathering job in parallel.  This combination is useful when you need to analyze large tables, partitions, or subpartitions.  This is accomplished  using a combination of the job scheduler, advanced queuing and resource manager.  Concurrent statistics collection can reduce the time it takes to gather statistics, provided the system can accommodate the extra workload.

Functionality wise, it is a way to gather stats on multiple tables, table partitions or subpartitions at the same time.

From a user perspective, the concurrent statistics collection functionality is very simple.  You set the CONCURRENT global preference to the required value using the DBMS_STATS package.  The RDBMS determines if concurrency is appropriate and if so, the level of concurrency to use. 
See MOS Note: 2034376.1, How to avoid ORA-06512 and ORA-20000 when Concurrent Statistics Gathering is enabled. New in 12.1 Database, Concurrent Statistics Gathering, Simultaneous for Multiple Tables or Partitions

Tuesday Nov 19, 2013

Oracle Demantra Gathering Statistics on Large Partitioned Tables in 11gR2

Hello!   Have you implemented partitions on a large Demantra table?  Are you using RDBMS version 11gR2?  Then consider implementing incremental statistics.

For all 11gr2 environments with large partitioned or subpartitioned objects turn on incremental statistics using this command:

exec dbms_stats.set_table_prefs('OWNER','TABLE','INCREMENTAL','TRUE');

Once this is set for any given table we should gather statistics on that table using the normal tool (fnd_stats in ebs or dbms_stats elsewhere). This first gather after turning it on will take longer than previous analyzes. Then going forward we will see the following :

1 – the normal dbms_stats (or fnd_stats) will only gather statistics on lower level partitions if the statistics on that partition are stale. This is a significant change. That is going forward using the default options of a gather command may in fact perform no reanalyze on the actual data if the modifications to the table don’t warrant it.

2 – if a subpartition is stale the normal stats will ONLY gather statistics on that subpartition. The partition for that subpartition will be re-derived as will the global statistics – no other statistics will be gathered.

Making this change promises to reduce gather stats by hours in some cases.

 

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