Defining the logical link

You can define the logical link definition statically by using the MSLINK system definition macro or dynamically by using the type-2 CREATE MSLINK command. Both methods enable you to name the link, associate the logical link with a logical link defined in a partner system, and define the type of physical link the logical link can be used with.

You can assign a name to the logical link by using the macro label field. Logical link names are used by the type-2 commands QUERY MSLINK or UPDATE MSLINK to identify the target logical link. If you do not define a logical link name using a macro, IMS assigns the default logical link name DFSLxxxx, where xxxx is the logical link number.

You associate the logical link with the logical link defined in a partner system by specifying a 2-character alphanumeric partner ID on the PARTNER keyword. The partner ID that you specify must match a corresponding partner ID specified in an MSLINK macro in the partner system. The matching values of the PARTNER keyword represent a logical connection between the two partner systems. For example, if B1 is defined as the partner ID in one logical link, this same B1 partner ID must be specified in the corresponding MSLINK macro of the partner system.

You match the type of physical connection that can potentially be used with this logical link by specifying the MSPLINK keyword. Depending on the type of physical link you specify, you can assign one or more MSLINK macros to the physical link:

  • When the physical link type is CTC or MTM, one MSLINK macro exists for each kind of physical connection.
  • When the physical link type is TCP/IP or VTAM®, multiple logical links can be assigned to one physical link. For example, System_B and System_C can have two logical links, one using MTM and the other CTC; System_C and System_D can have two logical links, both of which use one TCP/IP or VTAM physical link.

You can define a maximum of 999 logical links for each IMS system.

You can also define the logical link by using the type-2 CREATE MSLINK command instead of using a macro.

You can change logical link attributes that are defined by the MSLINK macro by using the UPDATE MSLINK command. The attributes you can change include the name, the physical link assignment, the partner ID, the buffer size, and others. The changes remain in effect until the next cold start of the IMS system.