How to remove DSNBs that have been used at one time, but are currently in the free chain.

Document ID : KB000030101
Last Modified Date : 14/02/2018
Show Technical Document Details

You can't remove DSNBs that have been used with the TMSXTEND utility program.

If you need to do this, you will have to use TMSSPLIT to export all of the tape volumes and associated DSNBs, format a new TMC with the reduced amount of DSNBs, and then run TMSMERGE to rebuild the entries.

 

The below procedure has been updated as well for those sites using an Extended Format TMC.

 

Internal Split/Merge Procedure for an Extended Format TMC

In the event the DSNB allocation contains a disproportionately high number of unused DSNBs, and there is no anticipation of future growth, it is possible to reduce the allocation by performing a split/merge operation.

The following process must be executed in an environment with no tape processing occuring, and no CA 1 batch or online processing being performed:

  1. Stop tape processing on all CPUs.
  2. Request the DBS subtask to RELEASE the TMC data set through the CTS address space commands.  (CTS is an optional task for CA 1 and you may not be running it.)

Note: For information, see the Administration Guide.

  1. Execute TMSCOPY to backup the TMC and Audit data sets.
  2. Execute TMSPTRS and correct any reported chaining errors.  Correct the chaining errors.
  3. Execute TMSCOPY to backup the TMC and Audit data sets.
  4. Allocate a target TMC on a device other than the current TMC and Audit data sets.
  5. Execute TMSBLDVR to map the target TMC.

The TMSBLDVR SYSIN control statements must specify all volume ranges in the production TMC, and the desired reduced number of DSNB records you wish to allocate.

i)                    Specify ‘PARM=NEW’

 

            NEW

When this parameter is specified, a new TMC is formatted without copying volume ranges or DSNB records from an input TMC. The new TMC must be preallocated and cataloged. CA 1 does not have to be active or batch active to run with PARM=NEW.

 

ii)                  The ‘//TMCNEW DD’ specifies a preallocated  new TMC data set.

 

TMCNEW

This DD statement is required if PARM=NEW is specified. A newly allocated, empty TMC should be specified.

 

  1. Execute TMSSPLIT. The list of volume serial numbers presented to TMSSPLIT should contain each volume serial number contained in your production TMC.
  2. Rename your production TMC to a backup name, and the target TMC to the production name.
  3. Execute TMSINIT to activate CA 1 and establish the target TMC as the active database.
  4. Request the DBS subtask to OBTAIN the TMC data set through the CTS address space commands.
    (CTS is an optional task for CA 1 and you may not be running it.)
  5. Execute TMSMERGE using as input the export data set created by TMSSPLIT.
  6. Verify the results and, if acceptable, backup the newly created TMC with TMSCOPY.