Advanced Topics › Control and Checkpoint File Considerations › How You Allocate Control and Checkpoint Files › DASD Control File Placement

DASD Control File Placement

Where you place the CA MIM DASD control file can impact the performance of CA MIM, and subsequently, the performance of your entire complex. Each CA MIM address space serializes access to the control file volume through z/OS RESERVE/RELEASE processing.

Use the following guidelines when deciding on which DASD unit to place CA MIM Control Files:

• Do select a device that has no other data sets on it.
• Do select a device that is accessible by all systems in the MIMplex.
• Do select a device that is currently supported by IBM or other hardware vendors.
• Do select a device that is connected by four to eight channel paths from each MIMplex LPAR.
• Do select a device that is connected via FICON channel paths, rather than ESCON channel paths.
• Do select a device whose channel paths are not overly busy.
• Do select a device that has been excluded from CA ASTEX Performance I/O monitoring.
• Do select a device that has been excluded from CA Vantage SRM housekeeping VTOC scans.
• Do select a device that has been excluded from full-volume backup utility services.
• Do select a device that has been excluded from synchronous or asynchronous I/O mirroring.
• Do not select a device that is subject to dynamic PAVing and Multiple Allegiance processes in both of the following circumstances:
  • The MIMplex spans multiple sysplexes and
  • The device is defined to a single logical control unit (LCU)

Placing the CA MIM control file on DASD units that do not meet these criteria can negatively impact CA MIM performance and degrade MIMplex-wide system throughput.