Migrating Java Applications to HP-UX

HP-UX. If you are unsure of the settings, or some are not set (and relying on defaults), then collect the

GC details from the JVM running on Solaris using:

-Xloggc:loggc.solaris -XX:+PrintHeapAtGC

On HP-UX, set the -Xmx, -Xms, -Xmn parameters based on above values from Solaris, and set GC

policy to be the same as on Solaris.

Add the following to verify that your settings are comparable:

-Xloggc:loggc.hpux -XX:+PrintHeapAtGC

The PrintHeapAtGC outputs can be viewed in HPjmeter.

The following figure shows a sample screenshot of PrintHeapAtGC data in HPjmeter:

Figure 9 GC Summary panel from PrintHeapAtGC output

Migrating from IBM/AIX

The IBM JVM has a different set of GC policies than Hotspot. These policies rely on similar concepts

but do not map directly to the policies on Hotspot. Therefore, experimentation may be required to

optain optimal performance.

The following are GC policies available in IBM SDK 5.0:

-Xgcpolicy:optthruput

Optimizes for throughput (the default policy). Throughput is more important than short GC pauses.

The application is stopped each time garbage is collected.

-Xgcpolicy:optavgpause

Optimizes for pause time. Trades high throughput for shorter GC pauses by performing some of the

garbage collection concurrently, using a concurrent mark and concurrent sweep phase. The

application is paused for shorter periods.