Specifying the DFSMSdss DASD I/O buffering technique to use for dump

With a single START I/O instruction, DFSMSdss can read 1, 2, or 5 tracks at a time, or a complete cylinder from the DASD being dumped. The DUMPIO parameter of the SETSYS command identifies which DFSMSdss DASD I/O buffering technique to use and the number of tracks to read.

The command is:

  SETSYS DUMPIO(n,m)

where n indicates the DFSMSdss DASD I/O buffering technique for physical volume dump (using the BACKVOL command with the DUMP parameter or during automatic dump), and m indicates the value used for DFSMSdss logical dump (DFSMSdss specified as data mover on the SETSYS command).

The values used for n and m are:

Value: Meaning
1: DFSMSdss reads 1 track at a time
2: DFSMSdss reads 2 tracks at a time
3: DFSMSdss reads 5 tracks at a time
4: DFSMSdss reads 1 cylinder at a time

Note: If you specify DUMPIO without a value for m, then m defaults to the value specified for n.

If you do not specify the DUMPIO parameter on any SETSYS command, the DFSMShsm default for n is 1 and for m is 4.

In the example system, a buffer of 5 tracks is used, so the SETSYS command that is added to the ARCCMDxx member in each of the hosts is:

SETSYS DUMPIO(3,1)