DLI and BMP modes in FM/IMS

From FM/IMS, you can connect to an IMS database in either DLI (Data Language 1) or BMP (Batch Messaging Processing) mode. In general, you would choose to use DLI mode when you are working in a development or test environment and you want to be able to manipulate your own copies of the data without impacting upon a live environment. Typically, you would use BMP mode to connect to databases in a “live? or production environment, when it is important that multiple users can access and update the data at the same time.

In DLI mode, FM/IMS allocates the IMS database data sets in the TSO address space. The databases can only be updated by a single user unless you use the Internal Resource Lock Manager (IRLM). By using IRLM to govern your access in DL/I mode, several users can update the same databases. To enable multi-user access in DLI mode, you must make sure that your databases are allocated with DISP=SHR.

In BMP mode, the database data sets are allocated in the IMS Control Region, allowing multiple users to update the same databases.

The installation process for FM/IMS provides default IMS control information for each IMS subsystem that the FM/IMS administrator allows FM/IMS functions to access. For much of the control information, different values can be specified for BMP and DLI mode. The installation process also allows the FM/IMS administrator to specify whether you, the user, are allowed to override each default value that is specified. So, for example:

For a production subsystem, you may not be able to override any of the IMS subsystem settings.
For a test subsystem, you may be able to override the IMS settings used when the function is run in DLI mode, but not the IMS settings used when the function is run in BMP mode.
For a development subsystem, you may be able to override all of the IMS subsystem settings.