If a file is connected to RMS with the RMS global buffer DEFAULT
    option enabled, either a percentage (GB_DEFPERCENT) of the file
    is cached or up to GB_CACHEALLMAX blocks of it are cached,
    whichever results in a larger global buffer count. A percentage
    greater than 100 percent can be specified for GB_DEFPERCENT to
    provide growing room for a file in the global cache.

    Note that although a maximum cache size of %x7FFFFFFF is
    supported for an indexed file, sequential and relative file
    organizations are restricted to a maximum cache size of 32767.

    GB_DEFPERCENT is a DYNAMIC parameter.