DBMS_STATS.GATHER_SCHEMA_STATS Procedures

This procedure gathers statistics for all objects in a schema.

Syntax

DBMS_STATS.GATHER_SCHEMA_STATS ( 
   ownname          VARCHAR2, 
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')), 
   block_sample     BOOLEAN  DEFAULT FALSE, 
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'),
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')), 
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')), 
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL, 
   options          VARCHAR2 DEFAULT 'GATHER', 
   objlist          OUT      ObjectTab,
   statown          VARCHAR2 DEFAULT NULL, 
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE')),
  force             BOOLEAN DEFAULT FALSE);
   
DBMS_STATS.GATHER_SCHEMA_STATS ( 
   ownname          VARCHAR2, 
   estimate_percent NUMBER   DEFAULT to_estimate_percent_type 
                                                (get_param('ESTIMATE_PERCENT')), 
   block_sample     BOOLEAN  DEFAULT FALSE, 
   method_opt       VARCHAR2 DEFAULT get_param('METHOD_OPT'), 
   degree           NUMBER   DEFAULT to_degree_type(get_param('DEGREE')), 
   granularity      VARCHAR2 DEFAULT GET_PARAM('GRANULARITY'), 
   cascade          BOOLEAN  DEFAULT to_cascade_type(get_param('CASCADE')), 
   stattab          VARCHAR2 DEFAULT NULL, 
   statid           VARCHAR2 DEFAULT NULL, 
   options          VARCHAR2 DEFAULT 'GATHER', 
   statown          VARCHAR2 DEFAULT NULL, 
   no_invalidate    BOOLEAN  DEFAULT to_no_invalidate_type (
                                     get_param('NO_INVALIDATE'), 
   force            BOOLEAN DEFAULT FALSE);

 

 

Parameters

Table 103-30 GATHER_SCHEMA_STATS Procedure Parameters

Parameter Description

ownname	Schema to analyze (NULL means current schema)
estimate_percent	Percentage of rows to estimate (NULL means compute): The valid range is [0.000001,100]. Use the constant DBMS_STATS .AUTO_SAMPLE_SIZE to have Oracle determine the appropriate sample size for good statistics. This is the default.The default value can be changed using the SET_PARAM Procedure .
block_sample	Whether or not to use random block sampling instead of random row sampling. Random block sampling is more efficient, but if the data is not randomly distributed on disk, then the sample values may be somewhat correlated. Only pertinent when doing an estimate statistics.
method_opt	Accepts: FOR ALL [INDEXED | HIDDEN] COLUMNS [size_clause] FOR COLUMNS [size clause] column|attribute [size_clause] [,column|attribute [size_clause]...] size_clause is defined as size_clause := SIZE {integer | REPEAT | AUTO | SKEWONLY} - integer : Number of histogram buckets. Must be in the range [1,254]. - REPEAT : Collects histograms only on the columns that already have histograms. - AUTO : Oracle determines the columns to collect histograms based on data distribution and the workload of the columns. - SKEWONLY : Oracle determines the columns to collect histograms based on the data distribution of the columns. The default is FOR ALL COLUMNS SIZE AUTO .The default value can be changed using the SET_PARAM Procedure .
degree	Degree of parallelism. The default for degree is NULL . The default value can be changed using the SET_PARAM Procedure . NULL means use the table default value specified by the DEGREE clause in the CREATE TABLE or ALTER TABLE statement. Use the constant DBMS_STATS.DEFAULT_DEGREE to specify the default value based on the initialization parameters.The AUTO_DEGREE value determines the degree of parallelism automatically. This is either 1 (serial execution) or DEFAULT_DEGREE (the system default value based on number of CPUs and initialization parameters) according to size of the object.
granularity	Granularity of statistics to collect (only pertinent if the table is partitioned). 'ALL' - gathers all (subpartition, partition, and global) statistics 'AUTO' - determines the granularity based on the partitioning type. This is the default value. 'DEFAULT' - gathers global and partition-level statistics. This option is obsolete, and while currently supported, it is included in the documentation for legacy reasons only. You should use the 'GLOBAL AND PARTITION ' for this functionality. Note that the default value is now 'AUTO '. 'GLOBAL' - gathers global statistics 'GLOBAL AND PARTITION ' - gathers the global and partition level statistics. No subpartition level statistics are gathered even if it is a composite partitioned object. 'PARTITION '- gathers partition-level statistics 'SUBPARTITION' - gathers subpartition-level statistics.
cascade	Gather statistics on the indexes as well.Index statistics gathering is not parallelized. Using this option is equivalent to running the GATHER_INDEX_STATS Procedure on each of the indexes in the schema in addition to gathering table and column statistics. Use the constant DBMS_STATS.AUTO_CASCADE to have Oracle determine whether index statistics to be collected or not. This is the default. The default value can be changed using the SET_PARAM Procedure .
stattab	User statistics table identifier describing where to save the current statistics
statid	Identifier (optional) to associate with these statistics within stattab
options	Further specification of which objects to gather statistics for: GATHER : Gathers statistics on all objects in the schema. GATHER AUTO : Gathers all necessary statistics automatically. Oracle implicitly determines which objects need new statistics, and determines how to gather those statistics. When GATHER AUTO is specified, the only additional valid parameters are ownname , stattab , statid , objlist and statown ; all other parameter settings are ignored. Returns a list of processed objects. GATHER STALE : Gathers statistics on stale objects as determined by looking at the *_tab_modifications views. Also, return a list of objects found to be stale. GATHER EMPTY : Gathers statistics on objects which currently have no statistics. also, return a list of objects found to have no statistics. LIST AUTO : Returns a list of objects to be processed with GATHER AUTO . LIST STALE : Returns list of stale objects as determined by looking at the *_tab_modifications views. LIST EMPTY : Returns list of objects which currently have no statistics.
objlist	List of objects found to be stale or empty
statown	Schema containing stattab (if different than ownname )
no_invalidate	Does not invalidate the dependent cursors if set to TRUE . The procedure invalidates the dependent cursors immediately if set to FALSE . Use DBMS_STATS .AUTO_INVALIDATE . to have Oracle decide when to invalidate dependent cursors. This is the default. The default can be changed using the SET_PARAM Procedure .
force	Gather statistics on objects even if they are locked

Usage Notes

DBMS_STATS.GATHER_SCHEMA_STATS generates differing sampling rates on partitioned tables when you use the auto_sample_size constant. DBMS_STATS tries to determine an adequate sample size for each type of statistic, which is different for each table or column (and each partition, if partitioned). It starts with a sampling rate to get approximately 5000 rows and examines the result based on statistical equations. This process is repeated with increased sampling rate for unsatisfactory results.

In general, the number of distinct values column statistics requires the highest sampling rate among the others, especially when each distinct value repeats a small number of times.

When you use a specific value for the sampling percentage, DBMS_STATS honors it except for when:

• The result is less than 2500 rows (too small a sample) and

• The specified percentage is more than the certain percentage.

Statistics for external tables are not collected by this procedure.

Exceptions

ORA-20000 : Schema does not exist or insufficient privileges.

ORA-20001 : Bad input value.