Using multiple IMS systems at the same release level and environment

You can run multiple copies of IMS, with or without multiple systems coupling (MSC), in the same z/OS® system and execute them concurrently. However, adding MSC allows communication and sharing of work between IMS systems. If your environment includes multiple IMS systems at the same release level, several considerations related to system definition apply.

When using multiple copies of IMS at the same release level and environment, the following requirements and conditions apply (regardless of the operating system):

• A unique subsystem identifier is required for each IMS DB/DC, DBCTL, or DCCTL control region. Specify this parameter (IMSID) in the IMS procedure for IMS, or in the DBC procedure for DBCTL, and in the dependent address space procedures (IFP, BMP, and MPP) that override the value specified during system definition. The Parm Block member DFSPBxxx can also override the IMSID value specified during system definition. This value must not conflict with any subsystem identifier defined in the system, including other DB or DB/DC systems.
• Type 2 and Type 4 SVCs and the channel-end appendages can be shared.
• When using multiple copies of IMS systems at the same release level in the same z/OS system, you only need one copy of the Type 2 and Type 4 SVCs.
• All suffixed modules must be unique.

  Related reading: See the description of the SUFFIX= keyword of the IMSGEN macro in IMSGEN macro.

• DFSVNUCx modules are required to run different IMS control regions.
• You can store unique copies of module DFSVC000, and module DFSVNUCx for each IMS system in a partitioned data set (PDS), concatenated with and in front of IMS.SDFSRESL. Alternatively, you can have unique copies of DFSVC000 in a PDS as described, and separate other modules within IMS.SDFSRESL through the SUFFIX= parameter of the IMSGEN macro during system definition.
• Under the z/OS authorized program facility, authorize all libraries from which modules are to be loaded for the control region.
• IMS systems can use the same IMS.SDFSRESL data set regardless of the resources that are defined for each system.
• If systems share IMS.SDFSRESL, you can store DFSMDA definitions in separate, authorized PDSs concatenated with IMS.SDFSRESL or use the IMSDALIB feature.
• The following IMS data sets must be unique and separately allocated to each IMS control region:
  • IMS.QBLKS
  • IMS.SHMSGx
  • IMS.LGMSGx
  • IMS.IMSMON (IMS Monitor) if used
  • IMS.MSDBCP1 if used
  • IMS.MSDBCP2 if used
  • IMS.MSDBDUMP if used
  • IMS.MSDBINIT if used
  • IMS.RDS
  • Online log data sets (minimum of 3)
  • Write-ahead data sets (minimum of 1)

  To make these data sets unique for each IMS control region, you can use the NODE= keyword of the IMSGEN macro.

• Each IMS system must have its own terminal network and MSC network (if MSC is included).