Resynchronizing the application database
A production database cannot contain up-to-date information for the following reasons:
- A volume was restored from a full volume backup.
- A volume was removed from the system.
- The system was stopped while DASD files were created, extended, renamed, released, or deleted.
The RESYNC program processes each DASD volume individually. A volume is selected and all allocations to the volume are delayed while the VTOC is read and the appropriate applications are created or updated in the database.
The majority of the RESYNC elapsed time is spent performing I/O operations. RESYNC elapsed time for a volume can be roughly estimated by counting one I/O per data set and two I/Os each time a budget application is updated for a data set. Multiply the number of I/Os by the average response time for the DASD devices being used. Initially, a computation adjustment of 50 percent should be added to application for RESYNC CPU utilization and operating-system overhead. With time, you can develop a more-accurate range of computation adjustment for your site.
Individual volumes can be resynchronized with the active database. Before resynchronizing, evaluate the impact of delaying allocations on each of the volumes. Volumes with little activity probably can be resynchronized at any time with little, if any, impact. Volumes with high activity ideally should be resynchronized during a period of minimal activity to limit the impact.
The multivolume RESYNC feature of the application collector allows volume totals to be kept for each application. These totals make it possible to RESYNC individual volumes and maintain accurate application totals. If multivolume support is not selected and an attempt is made to RESYNC individual volumes, it is impossible to know what space was being tracked on these volumes prior to the RESYNC and inaccurate application totals may result.
For more information, see:
SGCRSYNC command
Use SGCRSYNC to resynchronize multiple volumes. Member SGCMTRJ1 in ?prefix.BBSAMP contains sample JCL for SGCRSYNC. The SGCRSYNC keywords are as follows:
Keyword | Description |
|---|---|
AUDITDSN | This keyword displays application information for each data set. |
AUDITVOL | This keyword displays the status for each volume. |
CLEAR | This keyword is used to clear volume totals in the database. Use this parameter to clear volume specific totals when the volume no longer exist on the system. The default is ALLVOLS. |
DELXVOL | This keyword requests removing from the database all volumes not known to the system and recalculation of affected application’s space totals. This process is performed prior to processing resynchronization of volumes requested by RESYNC keyword. |
INCLUDE()/EXCLUDE()/ALL VOLS | This keyword is used to select volumes; can include or exclude volumes using either a single volume serial or a single mask. For example, if you code RESYNC INCLUDE(BSD/,EMP/), the system finds only those volumes that start with the BSD/ mask and ignores the EMP/ mask. To code both, use separate INCLUDE statements. EXCLUDE control statements must appear after all INCLUDE control statements. |
[INCPOOL() | EXCPOOL()] | These parameters of control statements RESYNC and RESERVE specify requested volume selection based on SRM pool or pool name mask. |
[INCSTORGRP() | EXCSTORGRP()] | These parameters of control statements RESYNC and RESERVE specify requested volume selection based on SMS Storage Group or Storage Group name mask. |
[INCSPOOL() | EXCSPOOL()] | These parameters of control statements RESYNC and RESERVE specify requested volume selection based on SRM subpool or subpool name mask. |
MAXTASKS | This keyword controls the number of RESYNC tasks. |
RESERVE | This optional keyword controls use of volume reserves. The default value is ALLVOLS. Multiple RESERVE statements may be specified. |
RESYNC | This keyword selects volumes to be resynchronized. Multiple RESYNC statements can be specified. |
TASKS() | This keyword specifies the number of RESYNC tasks. The RESYNC tasks run simultaneously. Each task will RESYNC one volume at a time until all the selected volumes have been resynchronized. The default is 1 and the maximum is 16. |
Examples of control statements
The following examples illustrate several RESYNC control statements:
RESYNC all volumes using three RESYNC tasks.
RESYNC
MAXTASKS TASKS(3)RESYNC all volumes with volume serials starting with EMP. Three RESYNC tasks are used.
RESYNC INCLUDE (EMP/)
MAXTASKS TASKS(3)RESYNC all volumes with volume serials starting with EMP except EMP001. Ten RESYNC tasks are used.
RESYNC INCLUDE(EMP/)
RESYNC EXCLUDE(EMP001)
MAXTASKS TASKS(10)RESYNC volumes from Storage Groups with name starting with MINI.
RESYNC INCSTORGRP(MINI/)RESYNC volumes from pools with name starting with BABP.
RESYNC INCPOOL(BABP/)RESYNC excludes volumes from subpool named MAREK.
RESYNC EXCSPOOL(MAREK)