Control Center Operations Guide for VSE

Single User Mode (SUM) DBSPACE Reorganization

You can choose to run a DBSPACE reorganization in Multiple User Mode (MUM) or in Single User Mode (SUM).

In SUM, contention with other applications and users is eliminated. Storage used to support those users can be used to define additional directory or page buffers, resulting in better performance.

In SUM, you can bypass logging by specifying LOGMODE N. However, switching to logmode N will probably require an archive and a coldlog before the switch and another archive before switching back.

Before You Choose Single User Mode Execution

Review the DB2 Server for VSE & VM Database Administration manual to understand Single User Mode database

execution. Also, review the topics on choosing a logmode and switching logmodes. Control Center Single User Mode parameters are listed below:

Single User Mode Parameters

Parameter

Description

SUM?

Specify "1" (YES) to cause a Single User Mode job to be submitted. This parameter defaults to "2" (Multiple User Mode).

DATABASE DEFINITION PROC

Specifies the name of the procedure that contains the job control statements (DLBLs) required to access the database. This parameter need not be entered if the job control statements have been loaded into standard labels.

LOGMODE

Specifies the logmode you want Control Center to use during Single User Mode processing. You must enter a value. Valid values are:

• A - All database changes are logged and regular database archives are maintained.
• L - All database changes are logged and regular log archives are maintained.
• N - No database changes are logged.
• Y - All database changes are logged but no archives are maintained.

NDIRBUF

The number of 512-byte directory pages to be kept in storage. The bigger this value is, the better your database will perform until you run out of storage or cause excessive paging. |If specified, the value must be in the range |10--400000. This parameter is not required.

NPAGBUF

The number of 4096-byte data pages to be kept in storage. Again, bigger is better, within reason. |If specified, the value must be in the range |10--400000. Entry of this parameter is not required.

SUM processing requires that the database be ended prior to execution. |If you submit a SUM job for immediate execution, it will |fail. This is because the database server must be stopped when a SUM |job is run but has to be up when you run the Control Center function that |creates the job. So, you must delay the execution of the job from the |reader manually or by using the scheduling controls of DUETIME, DUEDATE, or |DUEDAY.

When a job step requires access to a database, the database is started and the application program is executed. When the application program ends, control returns to the database server and the database is ended. The database remains down until it is restarted. Remember that changing the logmode will probably force some combination of coldlogs, and log or database archives.

Figure 58 is an example of a Single User Mode REORGANIZE DBSPACE (Option 3).|These parameters were used when choosing the DBspace Reorganization |utility's option 3 (REORGANIZE DBSPACE): owner = PUBLIC, DBspace = |SAMPLE, REBIND PACKAGE = 1 (YES), UPDATE ALL STATISTICS = 1 (YES), DDL |STATEMENTS = 500. On the submit screen, these options were used: |SUM = 1 (YES), LOGMODE = N, NDIRBUF = 10, NPAGBUF = 10.