Language Environment (LE) runtime libraries

When C programs (including the z/OS® UNIX shell) are run, they frequently use routines from the Language Environment® (LE) runtime library. On average, about 4 MB of the runtime library are loaded into memory for every address space running a LE-enabled program, and copied on every fork.

CEE.SCEELPA

The CEE.SCEELPA data set contains a subset of the LE runtime routines, which are heavily used by z/OS UNIX. You should add this data set to SYS1.PARMLIB(LPALSTxx) for maximum performance gain. By doing so, the modules are read from disk only once and are stored in a shared location.

Note: Add the following statement to SYS1.PARMLIB(PROGxx) if you prefer to add the load modules into dynamic LPA (Link Pack Area):

LPA ADD MASK(*) DSNAME(CEE.SCEELPA)

It is also advised to place the LE runtime libraries CEE.SCEERUN and CEE.SCEERUN2 in LINKLIST, by adding the data sets to SYS1.PARMLIB(LNKLSTxx) or SYS1.PARMLIB(PROGxx). This eliminates z/OS UNIX STEPLIB overhead and there is reduced input/output due to management by LLA and VLF, or similar products.

Note: Add the C/C++ DLL class library CBC.SCLBDLL also to LINKLIST for the same reasons.

If you decide not to put these libraries in LINKLIST, then you must set up the appropriate STEPLIB statement in rse.env, as described in rse.env, configuration file. Although this method always uses additional virtual storage, you can improve performance by defining the LE runtime libraries to LLA or a similar product. This reduces the I/O that is needed to load the modules.