An SVC call, implemented using an operating system intercept, is issued out of OPEN to perform scratch verification and data set protection.
The TLMSOPEN module gains control, builds a CA TLMS type 6 transaction, and issues a TLMSQMGR SVC.
The TLMSQMGR module gains control, receives the transaction, and cross-memory posts TLMSMAIN.
TLMSMAIN is activated by the cross-memory post.
TLMSMAIN responds to the post by calling TLMSMSGQ.
TLMSMSGQ receives a copy of the transaction by calling the TLMSQMGR SVC and then calls TLMSUPDT for processing.
TLMSUPDT accesses the Volume Master File specified in the CTS procedure through routines in its copy of TLMSVMRW.
The VMF is accessed by volume serial number (VSN).
If the retrieved VMF record indicates that the volume is in scratch status, the record is updated to indicate that the volume is in use, and is written back to the VMF.
(Optional) A copy of the transaction is written to the Alternate Log file if the RECOVRY system option is set to ALTLOG.
TLMSMSGQ is notified that the transaction is successful (the use of this volume may proceed), or that it is unsuccessful (another volume must be selected).
In either case, the initiating task is posted to report the status of the transaction. In this case, OPEN is waiting for this post.
OPEN is activated by the post from TLMSMSGQ.
Using the return vector to OPEN, OPEN either proceeds or demounts the volume and tries again.
