Virtual Device Engine › Virtual Device Engine Implementation and Use

Virtual Device Engine Implementation and Use

The Virtual Device Engine of a CA Vtape subsystem can consist of up to eight Virtual Control Units, each one running in a separate subaddress space, and each one controlling a subset of the total Virtual Devices defined for CA Vtape. The number of controllers started is controlled by customizing the VTDRIVE member in the CA Vtape parmlib. If the VTDRIVE member is not customized to take advantage of the multiple Virtual Control Units, all Virtual Devices will run under a single subaddress space named SVTSAS.SVTnV1. If multiple Virtual Control Units are defined, the subaddress spaces will be named SVTSAS.SVTnVm, where n = the subsystem number and m = 1 to 8.

All console commands issued to CA Vtape are issued to the SVTS started task. Subsequent communications between the SVTS and the SVTSAS started tasks in a subsystem are done using system MODIFY (F) commands.

During shutdown, the subsystem will stop the SVTSAS subaddress spaces.

If multiple controller subaddresses are active and one of these subaddress spaces needs to be stopped and restarted, you can use the SVTn Restart CU=n console command (where n = 1-8). This process is completely safe and independent of all other subsystem processes. Virtual Devices under the control of other Virtual Control Units and Backstore Engine physical tape processes are not affected.

When the subsystem detects a RESTART CU command, it does the following tasks:

• Gracefully stops all Virtual Device tasks in progress for the designated Virtual Control Unit.
• Restarts the corresponding SVTSAS subaddress space.
• Resumes the previous Virtual Device tasks in progress.

You should expect to see the following messages when restarting SVTSAS.SVTS1V1:

SVT1 RESTART CU=1 
SVT1X0101I Command Scheduled in SVTS 
SVT1X0100I Command Complete 
SVT1A0001I SVT1V1 Stopping 
IEF404I SVTSAS - ENDED - TIME=11.19.02 
$HASP395 SVTSAS ENDED 
$HASP100 SVTSAS ON STCINRDR 
$HASP373 SVTSAS STARTED 
IEF403I SVTSAS - STARTED - TIME=11.19.03 
SVT1A0000I SVT1V1 Ready 

The SVTn Restart CU=n console command affects all the Virtual Devices under the Control Unit being restarted. If only one Virtual Device needs to be restarted, use the SVTn Restart Unit=devn console command.