CA Disk is not using the Synchronous mode copy SS of the TS7700.
Our SYNCDEVS sysparm determines when we issue the SYNCDEV I/O command – not the Synchronous mode.
The SYNCDEVS sysparm determines if the SYNCDEV CCW is to be issued during Backup or Archive after every data set or if the disposition processing of data sets will be deferred until the final data block of the n-th data set is moved from the control unit to the media.
A SYNCDEV CCW will be issued to the device if the number of queued data sets exceeds the number specified.
A value of Y (or N01 or N00) will cause CA Disk to issue the SYNCDEV during tape processing after every data set.
A value of e.g. N10 causes CA Disk to issue the SYNCDEV during tape processing after every 10 data sets.
The default of N99 causes CA Disk to create a table of 99 entries. When the table fills up, then a SYNCDEV for all tapes (primary and copy) is issued and then all data sets are disposed of.
The disposition process completes the Archive/Backup by writing the DSNINDEX record, deleting/recatalog the data set if requested (like Archive), or updating the FMT1 change bit for backup and releasing the data set ENQ.