When RSS_FLOW_CONTROL or SDS_FLOW_CONTROL are set to a value other than -1 Informix will try to limit log activity on the primary server so that the secondary servers do not fall too far behind. There is no easy way to know or report on when this occurs.
For RS secondaries the only way to know if flow control is active is to look at the output of "onstat -g rss verbose".
For SD secondaries I see no documented method.
We have thousands (6,000) of users each with multiple sessions tending to our customers.
Our work around has been to disable RSS_FLOW_CONTROL to avoid performance issues on our production host and have noticed fewer complaints of slow downs since doing so.
A query was written to monitor if flow control was active but the sample rate would be to slow to always know when the issue was occuring.
The suggested corrective solution would be for the engine to clearly state when flow control is active.
|Who would benefit from this IDEA?||As a customer I should be able to easily see when replication is causing production slowness across our user base.|
How should it work?
Clearly state via one or more of the following actions that flow control is active:
1) Output on the Engine Status line:
IBM Informix Dynamic Server Version 12.10.FC8W1X4 -- On-Line -- Up 1 days 11:17:27 -- 311579232 Kbytes
Flow Control: RSS
2) An Alarm Event every time flow control is active with at least an ALARM_ATTENTION (3) as this is effecting production performance.
3) Message in the Message or Console log when the Instance has active flow_crontol.
05/25/20 13:16:50 Dynamic Server Flow Control Active. RSS
05/25/20 13:16:56 Dynamic Server Flow Control Enactive.
05/25/20 13:16:56 Flow Control Active for 5.400
|Priority Justification||Without this being part of the engine there is no way to effectively know when this is active.|
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