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)