Where does Ignition store Realtime or short term data? I know it will store data long term in a DB but how does it handle short term or realtime data? Does it send realtime data directly to the DB or is there a buffer or built in DB for this purpose?
Current values are in memory. That is the “tag”. Everything else goes to the DB. When there are connection problems, data may be buffered in the store and forward system. The S&F does not contribute to trend graphics, though, last I knew.
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Thank you. I just wanted to make sure that the short term buffer and S&F wasn’t relying on some internal DB structure to execute.
Store and forward uses RAM for a small buffer, and gateway-local files for a somewhat larger buffer. Precise behavior is an undocumented implementation detail, but is independent of the DB connection itself.
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Fair enough.
Also note that the standard tag historian (“tall” tables) always uses the store and forward system. The SQL Bridge module’s Transaction Groups (“wide” tables) are configurable per group whether to route through the S&F system. Scripting can submit database inserts directly or through the S&F system at the programmer’s discretion.
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Perfect. Thank you for that as well.