When allocation processing for a new data set occurs at the operating system tape selection exit (Subsystem Interface 78), CA Vtape decides whether or not to intercept the allocation by accessing Data Set Name Filters and Data Class Filters.
Note: For more information about filters, see the chapter "Tape Mount Intercept Filters" in the Configuration Guide.
If the data set to be written matches an entry in the selection filters, CA Vtape marks all devices, except the Virtual Devices, ineligible in the Eligible Device List (EDL). If no matching entry is found in the selection filters, the Virtual Devices are marked ineligible. The System Resources Manager (SRM) then selects an eligible device from the modified EDL to service the allocation request.
If the esoteric or generic specified in the UNIT parameter does not contain Virtual Device addresses, CA Vtape leaves the EDL unmodified.
If the UNIT parameter contains a specific device address defined as a CA Vtape Virtual Device, this device address will be used whether or not the data set matches an entry in the selection filters. CA Vtape is forced to service the mount request.
Note: Oracle's HSC, CSC, and SMC software also modify the EDL to influence tape allocation requests. If this software is not modified for the presence of CA Vtape, it can prevent CA Vtape from intercepting any allocation request by always marking the Virtual Devices ineligible. For the appropriate Oracle software changes, see the chapter “System Setup” in the Configuration Guide.
After SRM selects a Virtual Device for a new tape data set, the Virtual Device Engine detects the actual mount request, acquires the necessary space from the DASD buffer pool, and creates the Virtual Volume dataspace.
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