Be careful when tuning your storage class ACS routines to match the mixture of volume capabilities assigned by your storage group ACS routines. For example, if you have both cached and noncached 3390-3 in the assigned storage groups and your ACS routine assigned the same storage class (MSR=25) to all data sets, the noncached volumes are preferred over the cached volumes. This results in the noncached volumes being overused and the cache-active volumes are not selected until all the noncached volumes are above high threshold. If an MSR=2 is specified, then the cached volumes are overused.

This also holds true for other attributes. If you always assign ACCESSIBILITY=PREFERRED, then concurrent copy volumes are overused.