DB2 & IMS

Preparing for IMS 24x7 Availability

5 Pages

There are six considerations to change a DLI batch job into a BMP job:

  • The executing JCL must be modified.
  • The Program Specification Block (PSB) may need to be modified.
  • The program code may need to be modified.
  • An APPLCTN macro may need to be created.
  • An ACB may need to be created.
  • Modifications to access other mainframe subsystems.

The “may needs” depend on how the application’s components are currently configured. Some jobs only required JCL modifications because the other items were already compatible with the BMP requirements. A job trail can have a mix of DLI and BMP jobs, so not every job must be converted simultaneously and not every required change must be made in the aforementioned order.

The JCL

IMS batch jobs, whether DLIs or BMPs, execute the IMS region controller program DFSRRC00. The parameters passed to that program identify the type of job to be executed.

Figure 1 shows the IBM-provided sample JCL for DLI and BMP jobs. The first parameter in the PARM for DFSRRC00 identifies the type of job, either DLI or BMP. (It can also indicate a transactional message region, MSG, or DBB.) Changing that parameter, currently “DLI” to “BMP,” is the first step. This can be specified with a symbolic override, but more commonly, separate procedures are created because the validity of the remaining parameters depends on the job type. Therefore, permitting an override of that parameter would cause the job to fail unless other parameters are changed or removed.

 

There are 20 parameters that need to be removed from the DLI JCL and 11 that need to be added, either explicitly or by default. Some of those 11 aren’t specifically required for a BMP, but must be accounted for in the PARM for any dependent region. A few of the others will change meaning when specified in a BMP. For example, the IMSID in a DLI job is an identifier of messages written to the system log. In a BMP, it’s the four-character IMS subsystem id specified in the SYS1.PARMLIB member and identifies the IMS subsystem that the BMP will connect to.

PARM values are positional, so they must be accounted for by commas, if not specified. If defaults are taken, the values specified for the control region may become the defaults rather than what’s stated in the manual, so review those values. Also, each BMP job JCL is independent of every other one, so the parameters can be defined differently for each, if necessary.

Due to the large number of parameters, you may wish to review the detailed descriptions, which can be found in IMS Installation Volume 2: System Definition and Tailoring.

The other job change is to remove the Data Definition (DD) card for the IEFRDER (and IEFRDER2 if there is one) log data set and any database recovery steps. Since the control region will manage logging, backout and recovery, neither the log data set nor the backout steps are needed in the BMP job.

5 Pages