Wednesday, July 18, 2012

Gather Schema Statistics How to Use it !!!!

Gather Schema Statistics program generates statistics that quantify the data distribution and storage characteristics of tables, columns, indexes, and partitions.

As a general rule, run Gather Schema Statistics under the following circumstances:
1.  After there has been a significant change in data in either content or volume.
2.  After importing data.
3.  Any time end-users notice deterioration in performance in routine day-to-day business transactions or when running concurrent programs.
 4.  Run on a regular basis (weekly at a minimum) and anytime after application of patch, conversion, etc.

Type :

  1. GATHER_INDEX_STATS, Index statistics
  2. GATHER_TABLE_STATS, Table, column, and index statistics
  3. GATHER_SCHEMA_STATS,Statistics for all objects in a schema
  4. GATHER_DICTIONARY_STATS,Statistics for all dictionary objects
  5. GATHER_DATABASE_STATS,Statistics for all objects in a database
Example :

 (ownname => 'Scott', 
 estimate_percent => dbms_stats.auto_sample_size E "sample_size",
 options => 'GATHER EMPTY'
The above call starts the gather_schema_stats for a schema called SCOTT with estimate_percent at default sample size and options gather empty which gathers statistics on objects which currently have no statistics.

You can disable automated statistics collection job using the code below :
EXEC dbms_scheduler.disable(’GATHER_STATS_JOB’);
 To re-enable the job:
EXEC dbms_scheduler.enable(’GATHER_STATS_JOB’);
 To check if it job running or not 

Thank you 
Osama mustafa 

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