SAP ABAP Data Element DB2MOD_STAT_AGE (AGE parameter of MODIFY STATISTICS utility)
Hierarchy
☛ SAP_BASIS (Software Component) SAP Basis Component
   ⤷ BC-DB-DB2 (Application Component) DB2 for z/OS
     ⤷ STU2 (Package) CCMS for DB2 for OS/390
Basic Data
Data Element DB2MOD_STAT_AGE
Short Description AGE parameter of MODIFY STATISTICS utility  
Data Type
Category of Dictionary Type     Direct Type Entry
Type of Object Referenced     No Information
Domain / Name of Reference Type      
Data Type INT4   4-byte integer, integer number with sign 
Length 10    
Decimal Places 0    
Output Length 11    
Value Table      
Further Characteristics
Search Help: Name    
Search Help: Parameters    
Parameter ID   
Default Component name    
Change document    
No Input History    
Basic direction is set to LTR    
No BIDI Filtering    
Field Label
  Length  Field Label  
Short 3 AGE 
Medium 20 MODIFY STATISTIC AGE 
Long 34 AGE parameter of MODIFY STATISTICS 
Heading 42 AGE parameter of MODIFY STATISTICS utility 
Documentation

Definition

DB2 V7 RUNSTATS includes a new option, HISTORY. If specified, every time the corresponding catalog tables are inserted or updated, some selected fields are copied to some new catalog history tables. This results in preserving the relevant statistics data across multiple RUNSTATS executions and creates a basis for monitoring the database objects growth and assistance in determining optimal allocation quantities. Additionally, the historical data could be used for reinstating old catalog statistics in case of access path degradation.

There's a utility named MODIFY STATISTICS to clean up the statistics history catalog tables that can grow considerably large, if you run RUNSTATS as frequently as recommended. MODIFY STATISTICS has a parameter AGE that can be maintained here. Valid values are from 0 to 32767. MODIFY STATISTICS deletes all records older than the specified number of days. If you specify 0, MODIFY STATISTICS will not be used.

Recommended value

Since SAP does not yet use the HISTORY option of RUNSTATS, the recommended value is 0. If you have updated the RUNSTATS skeleton to use the HISTORY option, then the recommendation depends on your usage of the data:

  • If you just want to use the historical data for reinstating old catalog statistics in case of access path degradation, a value of 30 will be sufficient (If you haven't noticed the performance degradation until then, it can't hurt too much :-).
  • If you want to monitor database objects growth, a value of 1 to 2 years (i.e. 365 resp. 730 days) is more appropriate.

History
Last changed by/on SAP  20130604 
SAP Release Created in 700