I was wondering, when you use SQL tags in driven mode, does all tags using driven mode get read or does only the tag being used get read?
Example: Have 78 SQLtags which read in from the PLC’s the accumulated value. They are currently set to direct mode, the screen in question only shows one accumulated value at a time, user selected, if I change it from direct to driven and use a bit on the screen to enable the driven, will it attempt to read in all 78 tags or will it only read in the one currently being displayed?
Hope I have made this clear. Thanks and have a great day
I think you mean “leased” mode. However, ultimately both leased and driven scan classes operate in similar ways, just with different things driving them.
Everything is done on the scan class level. If you have a leased scan class with 78 tags and only 1 tag on screen, ALL of the tags are executed at the quicker rate.
This was done primarily for performance reasons in regards to the database, and mostly with an eye towards remote, satellite linked systems that are usually all on or all off, or at least easy to break up by screen. We recognize that in other situations it’s hard to put your tags into neat little groups on a screen by screen basis, because usually tags are used in multiple places. In the future we will be looking to address this and offer tag-level optimizations.