Storing libraries and modules in system memory

One way to boost performance is to load common or reusable modules into memory. For example, placing the Language Environment Library in a link pack area (LPA) can increase the performance of your entire system. This is recommended if your z/OS® system contains many applications that use the Language Environment Library, or is a heavy user of z/OS UNIX. LPAs store reentrant routines from system libraries. This saves loading time when a reentrant routine is needed. Individual modules can also be loaded into a single LIBPACK, in order to reduce the time that would otherwise be needed to load the individual load modules. For instructions for placing Language Environment Modules in Link Pack and LIBPACK, see z/OS Language Environment Customization.

If LPAs or LIBPACKS do not have enough space for the Language Environment Library, then you can place it into a library lookaside (LLA). This reduces library I/O activity by keeping selected directory entries in storage.

Similarly, if your application uses C++ class libraries, then application performance may be increased by placing specific libraries in the LPA or the dynamic link pack area (DLPA). For example:

If the application is a heavy user of the C++ ANSI Standard Libraries, then place the 31-bit CEE.SCEERUN2(C128) or 64-bit CEE.SCEERUN2(C64) Language Environment runtime library in the DLPA.
If the application is using the non-XPLINK C++ standard library, then place the CEE.SCEERUN(C128N) Language Environment runtime library in an LPA.
If the application is a heavy user of the USL IOSTREAM libraries, then place the CBC.SCLBDLL Language Environment runtime library in an LPA (for non-XPLINK applications) or the CBC.SCLBDLL2 Language Environment runtime library in a DLPA (for XPLINK applications).