The RVA does not support parallel channels on subsystems that support PPRCOPY. RVA does not support cascading or FAILOVER/FAILBACK.
Primary and secondary volumes may either be members of a PPRCOPY pair or a dual copy pair, but not both, on a 3990-6.
An application system
volume (primary) can be copied to only one secondary volume
if
the volume does not have multi-target support
. A PPRCOPY volume can be only primary or
secondary; it cannot be used for both functions at the same time if the volume does not support cascading.
A 3990 Model 6 can be the application storage control for some volumes and the recovery storage control for other volumes at the same time.
ESCON paths established by PPRCOPY provide connections between two or more 3990-6s. Specifically, a single path can be established, in one direction, to transfer a volume or volumes from, say, storage subsystem A to storage subsystem B. The same logical and physical path established from A to B cannot be used to transfer data from B to A; however, a separate path can be established to transfer data from subsystem B to subsystem A.
PPRCOPY secondary volumes act much like 3990 dual copy secondary volumes in that no read or write access is permitted. IBM recommends that you vary the attached secondary volumes offline to all attached systems. The PPRCOPY secondary volume IDs are the same as those on the application system (primary) volumes.
On RAMAC Array DASD, the dynamic sparing feature of RAMAC Array DASD is automatically disabled when the RAMAC volume is a member of a dual copy or PPRCOPY volume pair.
VM Note: When operating as a guest under VM:
- All PPRCOPY volumes must either be dedicated volumes, or defined as fullpack minidisks (including DEVNO-defined minidisks).
- The VM guest directory must include an entry stating "STDEVOPT DATAMOVER=YES".
Adding DASD channel extenders to a PPRCOPY configuration to support longer distances can seriously degrade the performance due to the additional time added to each copy write I/O. IBM therefore does not generally recommend using DASD channel extenders with PPRCOPY.