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 (see OPTIONS), 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; see NUMBUFS for more information.)

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.