In October 2014, we delivered Oracle WebLogic Server 12.2.1 as part of the overall Oracle Fusion Middleware 12.2.1 Release and October 2015 we delivered the first patch set release 188.8.131.52. This week, the second patch set 184.108.40.206 is available. New WebLogic Server 220.127.116.11 installers are now posted on the Oracle Technology Network and Oracle Software Delivery Cloud, and new documentation has been made available. There are a couple of new datasource features hidden there. One of them is called “gradual draining.”
When planned maintenance occurs on an Oracle RAC configuration, a planned down service event is processed by an Active GridLink data source using that database. By default, all unreserved connections in the pool are closed and borrowed connections are closed when returned to the pool. This can cause an uneven performance because:
· New connections need to be created on the alternative instances.
· A logon storm on the other instances can occur.
It is desirable to gradually drain connections instead of closing them all immediately. The application can define the length of the draining period during which connections are closed. It is configured using the weblogic.jdbc.drainTimeout value in the connection properties for the datasource. As usual, it can be set in the console, EM, or WLST. The following figure shows the administration console.
The result is that connections are closed in a step-wise fashion every 5 seconds. If the application is actively using connections, then they will be created on the alternative instances at a similar rate. The following figure shows a perfect demonstration of draining and creating new connections over a 60 second period using a sample application that generates constant load. Without gradual draining, the current capacity on the down instance would drop off immediately similar to the LBA percentages and connections would be created on the alternative instance as quickly as possible. Read the complete article here.
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