Researching ADF 12c Connection Threshold Property Functionality

ADF 12c developer guide describes new ADF BC tuning property - Disconnect Application Module Upon Reaching Maximum Connection Threshold (jbo.ampool.connection_threshold). I was doing a bit of research around this property and testing how it works. It looks to me - it doesn't work yet, as it should. You should be careful using jbo.ampool.connection_threshold. As per developer guide, connection threshold functionality is enabled when threshold value is set to positive number. Once AM pool will grow more than this number, ADF BC will start disconnecting and releasing DB connections for the least used AM's. Disconnect will happen during AM pool cleanup, developer guide recommends to configure shorter pool cleanup interval (jbo.ampool.monitorsleepinterval). With normal ADF BC DB pooling enabled, disconnect will happen after each request. In theory connection threshold is supposed to optimize this and do disconnect only when exceeding configured threshold and during pool cleanup cycle. However this doesn't seem to work, at least based on my test.

My test was based on these tuning settings:


- Minimum Available Size changed to be 0, all AM instances will be cleaned

- Pool Pooling Interval changed to be 30 seconds. Meaning in 30 seconds interval AM pool cleanup monitor will wake up and try to disconnect AM instances exceeding connection threshold or inactive AM instances

- Idle Instance Timeout property is kept default 10 minutes on purpose, in order to force earlier disconnect from jbo.ampool.connection_threshold

- Disconnect Application Module Upon Release is not set. As it is stated in the developer guide, when positive threshold value is set - DB connection disconnect mode is set automatically (meaning no need to set it by yourself directly)

Connection threshold (jbo.ampool.connection_threshold) is set to be 3. Meaning when there will be more than 3 active AM's with DB connections, disconnect mechanism should start during next pool cleanup cycle:


I was running this test with 6 concurrent users, starting with the first user - completing first user actions and then starting with the next user. By the time 6th user starts his session, 30 seconds interval from the first user session was passed - pool monitor should disconnect exceeded number of connections - but this didn't happen. All 6 connections still remain reserved, with connection threshold set to 3 and pool monitor interval set to 30 seconds:


Here you can download sample application I was using for this test - ADFBCConnThresholdApp.zip. This tuning option looks to me very powerful for performance optimization and more optimal DB connection usage, hopefully it will be fixed soon and we could use it. Or may be my test was wrong, and it works already - let's see if we get more input regarding this tuning option.