The STOSPACE Utility

The STOSPACE Utility

The STOSPACE utility is executed on a STOGROUP or list of STOGROUP s. It populates the DB2 Catalog with table space and index data set DASD usage statistics. These statistics are culled from the appropriate ICF Catalog as indicated in the STOGROUP for which the STOSPACE utility is being executed. All space usage statistics stored in the DB2 Catalog are specified in terms of kilobytes (1024 bytes).

JCL to execute the STOSPACE utility for all storage groups known to the DB2 system is in Listing 34.6. The (*) in the JCL can be replaced with either a single STOGROUP name or a list of STOGROUP names separated by commas ( enclosed in parentheses).

Listing 34.6. STOSPACE JCL

 //DB2JOBU  JOB (UTILITY),'DB2 STOSPACE',MSGCLASS=X,CLASS=X, //          NOTIFY=USER //* //**************************************************************** //* //*                  DB2 STOSPACE UTILITY //* //**************************************************************** //* //UTIL EXEC DSNUPROC,SYSTEM=DSN,UID='STOSPACE',UTPROC=" //DSNUPROC.SYSIN    DD  *     STOSPACE STOGROUP (*) /* // 

STOSPACE Phases

The STOSPACE utility has three phases:

UTILINIT	Sets up and initializes the STOSPACE utility.
STOSPACE	Analyzes the VSAM catalog for each table space and index in the indicated STOGROUP s. Space utilization statistics are gathered, and the DB2 Catalog is updated.
UTILTERM	Performs the final utility cleanup.

STOSPACE Locking Considerations

The STOSPACE utility can be run concurrently with all utilities.

STOSPACE Guidelines

When running the STOSPACE utility, use the following guidelines to ensure effective storage management.

Run STOSPACE Regularly

The STOSPACE utility should be run weekly for STOGROUP s to which highly active table spaces and indexes are assigned. It should be executed at least monthly for all STOGROUP s defined to the DB2 system.

Be Aware of DB2 Catalog Updates Caused by STOSPACE

The STOSPACE utility updates the following DB2 Catalog tables and columns :

Table	Column
SYSIBM.SYSSTOGROUP	SPACEF or SPACE , and STATSTIME
SYSIBM.SYSINDEXES	SPACEF or SPACE
SYSIBM.SYSINDEXPART	SPACEF or SPACE
SYSIBM.SYSTABLESPACE	SPACEF or SPACE
SYSIBM.SYSTABLEPART	SPACEF or SPACE

If the storage space value determined by STOSPACE is too large to fit in the SPACE column, the SPACEF column is used.

If the SPACE column in the SYSIBM.SYSSTOGROUP table is after running the STOSPACE utility, consider dropping the STOGROUP , because no objects are currently defined for it. You can issue the following query to determine this:

 SELECT   NAME, SPACE, SPACEF FROM     SYSIBM.SYSSTOGROUP WHERE    SPACE = 0 ORDER BY NAME 

Be careful, however, if your shop uses DFHSM to automatically migrate inactive data sets to tape. Issue the following query to be sure that no objects have been defined to the STOGROUP s with a SPACE value of :

 SELECT * FROM   SYSIBM.SYSSTOGROUP ST WHERE  NOT EXISTS        (SELECT 1         FROM   SYSIBM.SYSINDEXPART IP         WHERE  ST.NAME = IP.STORNAME) AND    NOT EXISTS        (SELECT 1         FROM   SYSIBM.SYSTABLEPART TP         WHERE  ST.NAME = TP.STORNAME) 

If no objects are returned by this query, the STOGROUP s previously identified probably can be dropped. There is one more problem, however. If a STOGROUP used as the default storage group for an active database is dropped, future table space and index DDL must explicitly specify a STOGROUP rather than rely on the default STOGROUP for the database. This is not usually a problem because the recommendation is to explicitly specify every parameter when creating DB2 objects. You can use the following query to determine whether a STOGROUP is used as the default STOGROUP for a database:

 SELECT   NAME FROM     SYSIBM.SYSDATABASE WHERE    STGROUP = 'STOGROUP'; 

Monitor DASD Usage

Run the DB2 DASD usage queries (presented in Chapter 26) after successfully running the STOSPACE utility. This helps you monitor DASD used by DB2 objects.

Now that you have your DB2 Catalog in order, look at several other types of DB2 utilities in Chapter 35, "Stand-alone Utilities and Sample Programs."