IMS language interface module
You must generate a user language interface only if you intend to access two Db2 subsystems from the same dependent region.
To provide this access, the subsystem member (SSM) must contain one entry for each subsystem. Each entry contains a different subsystem ID and its associated language interface token (LIT). IMS provides the DFSLI macro to generate additional language interface modules with unique LITs. The general format of the macro is shown in the table below.
| Macro | Option | Meaning |
|---|---|---|
| DFSLI | TYPE | Specifies the type of subsystem that can be accessed through this language interface module. Db2 is the only value supported by this option |
| LIT | Defines a name (called LIT) to relate a language interface module with an entry in the SSM for the dependent region |
When an IMS application issues a Db2 request, IMS knows the target subsystem by the LIT used in the request. For example, consider the case of a dependent region accessing two Db2 subsystems (DSN1 and DSN2):
- You generate a language interface with LIT=SYS2 (DFSLI001).
- You define two entries in the SSM member. The first entry points to DSN1 with LIT=SYS1; the second points to DSN2 with LIT=SYS2.
- You link-edit applications accessing the DSN1 subsystem with the IMS-provided language interface (DFSLI000).
- You link-edit applications accessing the DSN2 subsystem with the user-generated language interface (DFSLI001).
Even though a region can communicate with two or more Db2 subsystems, an IMS application can access only one—the Db2 subsystem referred to in the language interface that is link-edited. You can alter the SSM to route application requests to a different Db2 subsystem.