NonStop Server for Java 4.2 Programmer's Reference

Specifies an adaptive size policy. This option applies only for a parallel collector and, therefore, is disabled.
If you specify this option, the JVM exits with the error: -XX:+UseAdaptiveSizePolicy option is not
supported on this platform.
-XX:+AggressiveHeap
Obtains the platform resources and configures the heap layout accordingly, uses parallel collector, and
enables AdaptiveSizePolicy option. This option applies only for a parallel collector and, therefore, is
disabled. If you specify this option, the JVM exits with the error: -XX:+AggressiveHeap option is not
supported on this platform.
Concurrent Low-Pause Collector
A concurrent low-pause collector is for tenured generation. This collector does most of the collection concurrently
with the application execution. This collector divides the collection into different phases and does some phases
concurrently with the application execution and others in "stop the world" mode. This collection technique does
not perform well as the default collector when the phases of the collection cannot run concurrently with the
application thread. This garbage collector, therefore, is disabled in NonStop Server for Java 4.
The following java command options that specify a concurrent low-pause collector are not valid for
NonStop Server for Java 4:
-XX:+UseConcMarkSweepGC
Specifies using the concurrent mark-sweep garbage collector. If you specify this option, the
JVM exits with the error: -XX:+UseConcMarkSweepGC option is not supported on this
platform.
-Xconcgc
Enables a concurrent mark-sweep garbage collector. This option is disabled. If you specify this
option, the JVM exits with the error: -Xconcgc option is not supported on this platform.
Incremental Low-Pause Collector
By careful bookkeeping, the incremental (also called train) low-pause collector collects just a portion of the
tenured generation at each minor collection. The collector tries to spread the large pause of a major collection over
many minor collections. In overall throughput, this collector is slower than the default tenured generation collector.
To use the incremental low-pause collector, specify the following java command option:
-Xincgc
Specifies using the incremental low-pause garbage collector.
GC Log Rotation
When GC logging is enabled using the -Xverbosegc or –Xloggc option, by default, the GC data is written to
a single log file of unlimited size. Starting with the NonStop Java 1.4.2 T2766H10^ABV release, NonStop Java
supports controlling the size and number of the GC log files. The GC log records are written into the specified
number of GC log files in a round-robin fashion. This allows GC data to be archived easily and helps to limit the
amount of disk space consumed by the GC log files. Log rotation is also supported when using zero-preparation
verbosegc.
To enable log rotation, use the following option with -Xverbosegc, -Xloggc, or zero-preparation verbosegc: