How to submit the UPDATE STATISTICS statement
You submit the UPDATE STATISTICS statement to CA IDMS/DB either online or through the batch command facility. If you submit it through the batch command facility, you should execute it through the central version, because the dictionary is updated as part of processing the statement.
Journal in local mode
If you are running CA IDMS/DB in local mode, you can journal while updating statistics.
These statistics are updated
When updating statistics for a table, the UPDATE STATISTICS utility also updates statistics about:
Which pages are examined
When you specify a percentage of less than 100 in the SAMPLE parameter, the UPDATE STATISTICS utility selects the pages to be examined from across the entire area. For example, if you specify SAMPLE 50, the UPDATE STATISTICS utility examines every other page throughout the entire area, rather than every page in the first half of the area.
UPDATE STATISTICS extrapolates the statistics
When calculating statistics based on less than 100 percent of the pages in an area, the UPDATE STATISTICS utility extrapolates the values for the entire area from the values based on the percentage examined. For example, if you specify SAMPLE 50, and the 50 percent of the pages that are examined in the area contain 80 rows of the table, the UPDATE STATISTICS utility assumes the table has 160 rows.
The statistics stored in the dictionary reflect the extrapolated values, not the raw data.
UPDATE STATISTICS for IDMSNTWK
When updating statistics for an SQL-defined schema that references the non-SQL-defined schema IDMSNTWK, the UPDATE STATISTICS utility will only process area DDLDML. If an area other than DDLDML is specified using the AREA clause, a warning will be issued indicating there are no tables to process.
UPDATE STATISTICS for native VSAM files
When updating statistics for an SQL-defined schema that references a non-SQL-defined schema containing native VSAM files, the job abends with error-message DB002300 and DBIO Error code 3077. The UPDATE STATISTICS module IDMSCOLS collects statistics of some information found on a BDAM DB page (for example, total space available count) that cannot be found on a native VSAM page. In this case, the DBIO Error code 3077 indicates that an attempt was made to run an invalid CA IDMS utility against a native VSAM file.
UPDATE STATISTICS for a non-SQL-defined schema
When updating statistics for an SQL-defined schema that references a non-SQL-defined schema, statistics are stored in the dictionary (DDLDML) where the non-SQL schema is defined. For a system-owned index key that does not contain group elements, statistics are kept for each index column. If the index key contains a group element, a DB003202 warning message is issued and only the statistics of the first index column are updated.
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