Mending the control data set

Recommendations:

Always run the MEND function on a VSAM copy of the control data set first. Taking a back up of the control data set is essential because the control data set is unusable if MEND processing fails for any reason.
Do not run the MEND function when DFSMSrmm is running on the same system and is using a control data set with the same name as the control data set that the MEND function is expected to correct.
Do not enable stacked volume support until all systems using the control data set are on a supporting release level.

You can use EDGUTIL VERIFY as described in Verifying the contents of the control data set to find most control data set errors. Obtain guidance from the IBM Support Center to use EDGUTIL MEND to fix the errors found in the DFSMSrmm control data set. When you use the EDGUTIL MEND function to fix errors for system-managed tape volumes, MEND updates the DFSMSrmm control data set from information from the TCDB and the library manager database.

You can also use the MEND function to enable stacked volume support as described in Setting up DFSMSrmm stacked volume support. MEND processing checks to see if you have enabled stacked volume support with the EDGUTIL UPDATE option STACKEDVOLUME(YES). DFSMSrmm then creates stacked volume information from the existing volume 'In container' values. DFSMSrmm marks the control data ready for stacked volume support if processing is successful.

Note: The SYSIN commands in Figure 1 can be used to select a subset of volumes.

During MEND processing, DFSMSrmm creates stacked volumes in the DFSMSrmm control data set that are marked as media type HPCT and recording format 128TRACK. DFSMSrmm obtains the media name from pool definitions defined using the DFSMSrmm parmlib member VLPOOL command. Start DFSMSrmm at least once with a parmlib member that contains the VLPOOL commands, before you run EDGUTIL, to ensure that EDGUTIL can use the VLPOOL information. DFSMSrmm marks the stacked volumes as 'Created during MEND' and obtains location information from the last volume in sequence that is found to be in the container.

After MEND processing completes, you might need to add or change some volume information. Use the RMM CHANGEVOLUME subcommand to set or change any information.