If the linked object and/or the libraries used are very large, with the result that a large number of I/O operations are required during loading, you should check whether it is possible or necessary to use DAB (Disk Access Buffer).
DAB permits such a considerable reduction in I/O operations on frequently accessed files that in extreme cases the runtime depends only on the CPU requirements.
A cache area must be selected for the load object which is the same size as the load object itself. This is particularly simple if the object is the only member of the library. You can then issue the command
/START-DAB-CACHING AREA=*FILE(FILE-AREA=<library>),CACHE-SIZE=*BY-FILE
to reserve a main memory area with the same size as the library. This is filled the first time the object is loaded, with the result that no time-intensive I/O operations are required for any subsequent load operations.
The cache areas for the libraries can generally be created smaller than the total size of the libraries, since it is generally the case that not all of the modules contained in the libraries will be dynamically loaded. In this case, the cache size must be specified explicitly (in KB or MB) when the /START-DAB-CACHING command is issued. It is possible to monitor the cache hit rate for each cache area using SM2 or the /SHOW-DAB-CACHING command. The hit rate should be at least 80%. If this is not the case, the size of the cache area must be increased.