option #3

ISAM file I/O caching



USupported on UNIX



As of Synergy/DE 10, all systems implicitly enable file I/O caching; system option #3 is automatically implied.

System option #3 enables ISAM file caching on all OPENs for Revision 4 and 5 ISAM files.

When system option #3 is set, or when you use the /cache qualifier in the OPEN OPTIONS string, the runtime performs three types of caching to ISAM files depending on how the file was opened:

In all cases, if the cache becomes full before a CLOSE or FLUSH is issued, the oldest blocks will be flushed. (The NUMBUFS environment variable determines the size of the cache.)

When you use ISAM file caching, an additional amount of memory and system resource is required for each file OPEN.

On Windows, ISAM file I/O caching is always enabled.