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Configure memory overload protection


Follow these instructions to configure memory overload protection from the administrative console.

 

Before you begin

Configure the autonomic request flow manager (ARFM). See Configure the autonomic request flow manager.

 

About this task

To protect against memory overload, MOP must initially discover the maximum rate, that is, calls per second, that can be sustained without exceeding the maximum percentage of the maximum heap size. As it is discovering the maximum rate, MOP slowly allows more traffic through without affinity, but will reject the remainder. Initially, a potentially large number of HTTP requests or SIP messages without affinity will be rejected with a 503 (unless the error code is changed). WebSphere Virtual Enterprise persists the maximum rate across server restarts, so it must discover the maximum rate once. The maximum rate can change over time due to changes in the session or dialog lifetimes, but these lifetimes generally change relatively slowly and MOP is able to react to such changes. When discovering the maximum rate, WebSphere Virtual Enterprise must keep the rate relatively steady for at least an averaging window. The averaging window must be at least as long as the lifetime of most of the HTTP sessions, SIP dialogs, or application sessions. Therefore, the longer the averaging window, the longer it will take to start.

MOP is disabled by default. To enable, follow these steps from the administrative console:

 

Procedure

  1. Expand Operational Policies > Autonomic Controllers > Autonomic Request Flow Manager

  2. Type a value less than 100 in the Memory overload protection: Maximum percentage of the WebSphere Application Server maximum heap size to use field.

  3. Expand Servers > Dynamic clusters ><dynamic cluster> Server template > Class loader > Process definition > Java Virtual Machine

  4. Set Generic JVM arguments to -agentlib:HeapDetect -Xgcpolicy:gencon -Xdump:heap:events=user.

 

What to do next



 

Related concepts


Memory overload protection

 

Related tasks


Configure the autonomic request flow manager

 

Related reference