Enqueues used during Backup of OPEN files.

Products

• Disk Backup and Restore - MVS
• DISK BACKUP AND RESTORE- ADD-ON OPTIO
• DISK BACKUP AND RESTORE

Issue/Introduction

What enqueues are used - or can be used - during Backup of OPEN files?

Resolution

FOR NONVSAM
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Disk needs to get a SHR enqueue to Backup files and an OLD enqueue for Archive. If an enqueue can not be obtained, that data set is bypassed and a message is displayed. 
There is a facility that can help capture those enqueued data sets with this Sysparm: ARCFDEFR
N (default) - Do not queue request.
Y - Queue a Deferred Archive/Backup request if Archive/Backup failed because the data set was in use.
Then, run the Deferred Archive job to try to get the backup or archive.
 
To not do any enqueues during Backups, specify this Sysparm: USERSENQ with value DMSNOENQ
DMSNOENQ is a module we provide that is used during auto restore. This is noted in the manual as: Integrity exposure
But, several users use it to get a copy of a data set even if in flight.
Note:  This facility can not be used for Archive processes.
 
If you use USERSENQDMSNOENQ, then you can add this sysparm: ENQADDTL
N (default) - Do not do an extra enqueue
Y - Will perform an additional enqueue on the QNAME SYSDSN to determine if the data set is in use.  If so, a message 3715 will be issued stating which data sets were in use at the time of the backup.
 
FOR VSAM
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This sysparm controls the enqueue level: VSALOSHR
N (default) - To allocate VSAM defined with SHR(1 3) with DISP=SHR, all others as 'OLD'.
Y - To allocate all VSAM 'DISP=SHR'. (Integrity exposure.)
  
To get a "perfect" copy of critical VSAM files that are always in use, refer into the BACKUPCC Command in the Disk tech doc.