DASD Config

DASD Configuration Analysis

Specifics - DASD Configuration analysis:

There are several things to remember with configuring the DASD environment:

Do NOT combine spool, paging, TDISK and minidisks at the volume level to avoid contention and overhead.
Do NOT have multiple page or spool allocations on the same volume.
Do NOT put TDISK on the same volume as other data that has a performance requirement.
Do NOT share z/OS and VM data at the control unit level to avoid error recovery complications and performance issues if z/OS runs I/O intensive batch jobs.
Verify each device has multiple channels.
Verify MDC is enabled appropriately. Some processes benefit from MDC, ZVPS does utilize it.

Note: In the ESADSD1 screen or report - if the Dev Addr (Device Address) and the SSID (System ID) are the same, either the monitor wasn't configured correctly (not done by the VSI setup) or the monitor configuration area is too small. This can happen part way through the screen/report, which means the configuration area is too small and the monitor records that have the device address have been lost.

ESADSD1 - Shows the current DASD configuration and characteristics.

Volser - This is the volser name. Often the name indicates what kind of data is on the device. IE - VM4P19 is a paging device on system VM4.

Device Type - This shows the DASD device type - ie a 3390-3 is a "Mod 3" device with 3339 cylinders.

Online CHPIDs - Shows what CHPIDs are associated with each device. Depending on the device type, there should be at least two CHPIDs per device. Some device types are ok to have one CHPID or can architecturally only handle one CHPID. Verify the expected number of CHPIDs are present/online.

Extent Type - If the device is a page/spool device, it will show it here. This is good to verify that page and spool devices aren't being shared with minidisks. Can also check the start/size to verify it is as expected.

MDisk links - This shows how many minidisks are currently on each device. Certain devices like paging or spooling, should not have minidisks defined.

MDC Elg - Indicates if this device is eligible for minidisk caching. MDC needs to be enabled for certain processes.