Using Library Lookaside under z/OS

As an alternative to IMS program loading with z/OS® Program Fetch, you can specify the use of the z/OS service Library Lookaside (LLA). LLA is the recommended method for managing dynamically loaded program libraries.

For IMS application programs, it saves load modules in a data space, so the modules can be retrieved more efficiently than through DASD. LLA monitors the frequency with which modules are accessed and readjusts its data space population to optimize the probability of having a module in the data space when it is requested.