Whether input caching is useful and significant to the analysis function depends on the type of input (image copy or area data set) and on the internal operating mode of the function.
The analysis function has two internal modes of operation: sequential mode and direct mode. Fast Path Analyzer/EP decides internally which mode is required, or which is more efficient, and executes accordingly. If the product performs the analysis function in sequential mode, any caching that is specified by using the ICACHE keyword is ignored.
Image copy input
Without caching, the analysis function must use sequential mode with image copy input.
By using the ICACHE keyword to specify IOVF caching, the analysis function can use direct mode, performing random input I/O against the cached CIs. If resources are not available, the analysis function ignores any cache request, generates a message, and continues in sequential mode.
If resources allow, caching of IOVF and SDEP allows the analysis function to perform more efficiently. SDEP control intervals are not processed randomly, but loading them into the cache at the same time as the IOVF control intervals reduces I/O against the image copy data set.
Area data set input
If the analysis function is using an area data set as input, using the ICACHE keyword to specify IOVF input caching can significantly improve performance by eliminating the random I/O to the IOVF control intervals.
Do not specify input caching of SDEP CIs. Because SDEP CIs are processed sequentially, caching provides no benefit and can slow the process.