[IOServer]CacheOptMode

This parameter is designed to reduce #COMs when using dialup or scheduled devices. The #COM is often a result of how tags are blocked together in the IOServer.

This is the global INI setting. This setting is allowed at a per device level by:

[<unitname>] CacheOptMode = x

By default, the IOServer only searches for tag data requests to be within or equal to a single cached tag set; for example, cache has tag address points 1 to 10, and then 11 to 20, and a request wants addresses 5 to 6, this is permitted. If, however, the request was for items 9 to 11, the system would not return a match and would request a read from the driver. For a disconnected dialup unit, this would cause a #COM or #WAIT.

CacheOptMode values are:

• 1 - First come first served - Tells the IOServer to search through cached points looking for the data, once it is found return.

• 2 - Scan cache for latest entries - Forces the scan to look through cached items to find data which is the MOST recent.

• 4 - An incomplete match is OK - Tells the system that if some items match and some are not found, to consider this OK.

• +8 - Allow behavior on all devices, by default the settings above only apply to remote units.

• +16 - Allow written data not to remove cache item and update value on return, e.g. 1 to 10 in the cache, write to 8. The default behavior would be to remove the whole cache item so that a fresh read of 1 to 10 would be needed on a write to 8. With +16 added, then 1 to 10 stays in the cache, and item 8 would be updated on the REPLY from the driver.

For dialup devices, CacheOptMode=1 covers the majority of needs.

Allowable Values:

• 0 - No login

• 1 to 31 - Combination of above values

Default Value:

0

See Also

IOServer Parameters