If you are not familiar with Core Group in WebSphere, check out our Core Group getting started article.
Let's say you have a large number of servers in a Core Group, such as 50 or more servers. If multiple servers in the Core Group are being restarted, and one of the servers experiences an OutOfMemory condition, and the following event is recorded in HPEL or SystemOut.log, other servers in the Core Group may fail to start.
CWRLS0030W: Waiting for HAManager to activate recovery processing for local WebSphere server
This can be fixed by creating the IBM_CS_OOM_ACTION=Isolate Core Group custom properties.