Multiple Systems Coupling concepts

MSC provides the ability to connect geographically dispersed IMS systems in such a way as to allow programs and operators of one IMS to access programs and operators of the connected IMS systems.

Communication can occur between two or more (up to 2036) IMS systems running on any supported combination of operating systems.

MSC also provides a way to extend the throughput of an IMS beyond the capacity of a single CPU. This extension is possible if the IMS applications can be partitioned among IMS systems two ways:
  • Horizontal partitioning: Applications execute in more than one IMS with database contents split between IMS systems.
  • Vertical partitioning: Applications execute in one IMS with the complete database that they reference attached to that IMS. Transactions can originate in any IMS.

A link is a connection between two IMS systems. All links must be defined during the IMS system definitions for each IMS. There are two types of links: physical links and logical links.

  • A physical link is the access method connection or hardware connection between two IMS systems.
  • A logical link is the mechanism through which a physical link is related to the transactions and terminals that make use of that physical link.

You can assign a logical link to a physical link during system definition or you can assign it dynamically by using the CREATE MSLINK command. You can also dynamically update the definition later by using either the IMS type-2 UPDATE MSLINK command or the type-1 /MSASSIGN LINK command.