Attempting to use SPACE CONSTRAINT RELIEF dataclas atribute allocation after a failed multi-striping allocation

To attempt SPACE CONSTRAINT RELIEF single-striping allocation after a failed multi-striping allocation.


As the level2 support had explained in PMR 50100,228,631 , when a multi-striped sequential dataset allocation fails ( Sustained Data Rate greater than 0 was specified in STORAGE CLASS and there is no sufficient space to satisfy the request in at least one stripe in the storage group ) then the SPACE CONSTRAINT RELIEF data class atribute cannot be used because SMS has already chosen its allocation path, the striping allocation path (i.e. IGDVTSTR), which do not consider space constraint relief.

But trying to use SPACE CONSTRAINT RELIEF after a failed multi-striping allocation could be successfull because it is easyer to obtain the original amount of tracks requested when there is no a requesite to have exactly the same number of tracks in each volume. SPACE CONSTRAINT RELIEF single-striped multi-volume allocation is less exigent than MULTI-STRIPED allocation.

So, the RFE target is to change the striping allocation path so that SMS tries a single-striped multi-volume allocation using SPACE CONSTRAINT RELIEF when the original multi-striping allocation fails. Or the equivalent, trying the non-striping allocation path after a failure in the striping allocation path.

The L2 Support considerations for PMR 50100,228,631 follow:

In the case where the data set is allocated as multi-striped (SDR is NOT 0 or blank), SMS uses the striping allocation path (i.e. IGDVTSTR) to allocate the data set. This path is where the reduction of stripes is performed. Even if we get to a single stripe in this case, we are still in the striping allocation path and this path will not consider space constraint relief.

In the case where SDR=0 or is blank implying a single striped data set is to be allocated, we do not go down the striping allocation path and this will use the non-striping allocation path which will consider space constraint relief if necessary.