Patching to force UCBs to be OBTAINed each time a volume is space checked

This patch causes the DFSMShsm space checking function to re-OBTAIN each DASD volume’s UCB prior to addressing fields within the structure. This prevents errors in an environment where dynamic I/O configurations are occurring and the user does not want to stop and start DFSMShsm.

Issue the following PATCH command to force the UCBs to be OBTAINed for each DASD volume processed during space checking:

PATCH .MCVT.+4F1 BITS(......1.)

Once it is known that no further dynamic I/O configurations will be occurring, this bit should be reset to OFF. Leaving this bit set on will impact the performance of your system. Issue the following PATCH command to set the bit OFF:

PATCH .MCVT.+4F1 BITS(......0.)