Leftover memory segments that are no longer needed are an ordinary byproduct of Java processing. Each JVM includes a feature that identifies and gathers these segments, making the virtual memory space available for later use.

Known as garbage collection, the tactics and details of this capability differ among JVM implementations from Sun Microsystems, IBM, and others. If such garbage collection is not run often enough or is not successful enough at recovering unneeded memory, the JVM may fail with an out-of-memory exception. This may indicate a design or implementation flaw, or may only indicate that demand for virtual memory under the current workload exceeds supply.

The Pega-RULES agent periodically forces some memory segments to be available for garbage collection, using the standard activity Code-.SystemCleaner.

JVMs can support verbose logging of garbage collection operations, allowing skilled IT staff to review and analyze details of memory usage. An optional prconfig.xml setting identifies the directory into which verbose garbage collection output. For example:

<env name="GarbageCollection/Logfile" value="C:/pegarules/logs" />

This directory must match the location supplied with the verbose GC option to the JVM.

Minimizing memory demand

Each Process Commander requestor's clipboard occupies virtual memory. Good clipboard management practices include:

• Releasing pages that are no longer needed with the Page-Remove method
• Limiting the maximum number of instances retrieved by an Obj-Browse method, list view, or summary view rule
• Retrieving only needed properties in an Obj-Browse method, Obj-List method, list view, or summary view rule

Using the Performance tool, you can monitor the size in bytes of your clipboard.

PEGA0028 Alerts

If garbage collection completes but fails to produce enough results, the system adds an alert of type PEG0028 to the Alert log.

PegaRULES Log Analyzer

This standalone Web application, available from the Pega Exchange can analyse GC logs. See PDN articles PRKB-25406 Understanding the PegaRULES Log Analyzer

Reduce garbage collection from SMA

On a multinode cluster, or on a production system with a single Process Commander node, install the System Management application on an application server (and JVM) separate from those where PRServlet runs. Even when the System Management application is lightly used, when sharing an application server it can cause frequent and unwanted garbage collection operations that can affect performance.

Additional resources

JVM settings can affect performance of your system. For guidance on JVM settings, use the Installation Guide for your platform, and see these Pega Developer Network articles:

• PRKB-25365 Understanding the PEGA0028 Alert
• PRKB-21028 Best JVM settings depend on vendor, version, and other factors.
• PRKB-23154 Tuning the IBM JVM 1.4.2 for performance
• PRKB-24141 Tuning the Sun JVM 1.4.2 and 5.0 for performance
• PRKB-24221 How to set up IBM JVM v1.4.2 and v1.5
• PRKB-24222 How to set up Sun JVM v1.4.2 and v1.5

	Java Virtual Machine, PegaRULES Log Analyzer
	About the Performance tool Page-Remove method Understanding Alerts

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