The maximum (or almost) of non-reserved SQL connections to the database are being used this can cause slowness or performance issues
In the debug logs you see the following warning/error:
"(YELLOW) Alert 1-DBC-xxxx: XX out of XX non-reserved SQL connections are being used"
"(RED) Alert 1-DBC-xxxx: XX out of XX non-reserved SQL connections are being used"
This indicated that ListManager is using the maximum (or almost) amount of non-reserved SQL connections to the database this can cause slowness and performance issues. We would advise to increase the SQL pool and Max threads.
The Max SQL Threads should be at least 20 below the SQL Pool. This is different than what was recommended in version 11.x and below. The default value for Max threads used to be 10, but it changed to 5 in v12.x, and the default SQL Pool remained at 25.
The new suggested values by Engineering team show below. There is no particular reason we suggest increments in 25, and the suggested SQL Pool you should use is based on what you see that your SQL Server can handle. It is possible to go higher if needed, but so far I have only seen customers go as high as 75 with any benefit.
SQL Pool / Max Threads
25 / 5
50 / 30
75 / 55
100 / 80
NOTE: The max threads value can be configured in the UI at Utilities : Administration : Server : Server Settings : Machine Settings > Limits.
The SQL Pool value can be configured in the lmcfg.txt file at the install directory.
Please restart the ListManager services after applying these changes to take effect.