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David Cleary
Guest
The good news is we just delivered this feature in OpenEdge 12.2. While it is important that you understand how many database connections your server will need based on how many sessions you have configured, the fact is other DB clients can take those away. To solve this problem, we have just introduced the PASOE Agent Self Management feature. This feature allows you to set how many available sessions should be available in an agent process. The default is 1. It works this way: The agent will ensure there is minAvailableSessions in an agent that is not servicing requests. If you have your maxSessions and numConnections set to 100, Sessions will be created as load increases. If you have 50 concurrent sessions servicing requests, the agent will have created an extra session that is available, so you will be at 51 actual sessions. As load continues to increase and you run out of database connections, eventually these spare sessions will be unable to be created. Let's say this happens at 75 sessions and the failure happens while trying to create session 76. Since this session is not servicing a request, no client will see the error. When the agent sees this, it will reduce the maxABLSessions down to 75, and will no longer attempt to create a session that fails. When dealing with multiple agents, it is important that they all be started initially with at least a single session. We found out late that if you are using this feature and the session manager attempts to start a new agent, that agent will fail due to its inability to create a single session. Since this feature is implemented in the agent itself, the session manager is currently unaware that it shouldn't be starting a new agent. We may address this in a future release, as well as anything else we get feedback on related to this feature. I expect we will be updating the tuning guide in the coming months to include this feature. Let me know if you have any questions on this feature, Dave
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