Modifying skeletal JCL members

IMS HP Change Accumulation Utility analyzes the output from GENJCL and creates multiple job procedures to run in parallel, one for each selected CA group.

Because multiple tasks are created to read the log data sets, the demand on the number of tape device units can exceed the number of available devices. Unnecessary waits would result until a tape device does become available.

The global parameter INLIM allows you to limit the number of log reader tasks that read log data sets in parallel. This parameter also limits the number of tape devices IMS HP Change Accumulation Utility uses.

However, before starting the change accumulation process, DBRC checks the availability of all log data sets and requires that the data sets and their devices be available even though the log read is done in a different address space.

IMS HP Change Accumulation Utility processing modifies the JCL to defer the mounting of tapes while DBRC is performing its checks. Also, to reduce the requirement for devices, you will need to modify your skeletal JCL member as follows:

• If the log data sets are on permanently mounted devices, no change is required.
• If all log data sets are on tape devices, ensure that your DFSULOG contains both DISP=SHR and UNIT=(%LOGUNIT,,DEFER).
• If the log data sets are stored on a combination of both tape devices and DASD, modify the skeletal JCL member so that the DASD log data set UNIT parameter definitions are unchanged and the TAPE log data set UNIT parameter definitions are modified. For example:

  %DELETE (%LOGUNIT EQ '3400')                                     
   //DFSULOG  DD  DSN=%LOGDSN,                                     
   //             DISP=SHR                                         
   %ENDDEL                                                         
    %DELETE (%LOGUNIT NE '3400')                                     
   //DFSULOG  DD  DSN=%LOGDSN,                                     
   //             DISP=SHR,UNIT=(%LOGUNIT,,DEFER),                 
   //             DCB=(BUFNO=32,RECFM=VB)                          
   %ENDDEL 
  

  In this example, if the log unit is 3400, the first DFSULOG DD statement is deleted, and the second one is kept. If the unit is not 3400, the first DFSULOG DD statement is kept, and the second is deleted. The value in the delete expression (3400, in the example) is where the log data resides. This is either the generic device name as registered with DBRC, or it is a name known to you when the log data set was created.

  For the specific JCL statements that are required for allocating the DFSULOG on both TAPE and DASD, see the HPCCAJCL sample member.