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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