Assigning relative importance to IMS address spaces

After setting performance objectives for IMS transactions, specify in WLM service classes the importance of each IMS address space relative to all other IMS address spaces. Using your specifications, WLM determines the processor dispatching priority for all address spaces in the z/OS® system.

In the following figure, the WLM ISPF-driven panel for defining a WLM service class assigns relative importance of 2 to the IMS control region address space.

Figure 1. Assigning importance using the WLM ISPF panel Modify A Service Class

                          MODIFY A SERVICE CLASS               ROW 1 TO 00000100
COMMAND ===> ___________________________________________________________00000200
                                                                        00000300
SERVICE CLASS NAME . . . . . : CNTL                                     00000400
DESCRIPTION  . . . . . . . . . IMS CTL RGN SERVICE CLASS                00000500
WORKLOAD NAME  . . . . . . . . IMS       (NAME OR ?)                    00000600
BASE RESOURCE GROUP  . . . . . ________  (NAME OR ?)                    00000700
CPU CRITICAL . . . . . . . . . YES       (YES OR NO)                    00000800
                                                                        00000900
SPECIFY BASE GOAL INFORMATION.  ACTION CODES: I=INSERT NEW PERIOD,      00001000
E=EDIT PERIOD, D=DELETE PERIOD.                                         00001100
                                                                        00001200
        ---PERIOD---  ---------------------GOAL---------------------    00001300
ACTION  #  DURATION   IMP.  DESCRIPTION                                 00001400
  __                                                                    00001500
  __    1              2    EXECUTION VELOCITY OF 70                    00001600
                                                                        00001700

The following table suggests how you might assign WLM importance values to achieve a recommended relative prioritization of some of the IMS address spaces.

Table 1. Assigning WLM importance to IMS address spaces
WLM importance	IMS address space
SYSSTC	IRLM, VTAM
1	CTL, DLI, DBRC, ICON, FDBR, CQS, SCI, OM, RM
2	ODBM, MPP, IFP, JMP, BMP, JBP
3 and 4	MPP, IFP, JMP, BMP, JBP, Batch

By prioritizing IMS address spaces as shown in the table, you minimize the risk of critical functions having to wait for dependent regions to finish processing before they receive the processor resources they need. Such critical functions include locking, DB authorization, IMSplex-wide command processing, messaging, and DB open and close activities.

Related reading: For additional information on dispatching priorities, see Dispatching priorities.