NonStop Server for Java 5.1 Programmer's Reference

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 5.1 T2766H51^ABW 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:
-XX:GCLogLimits=M,N
where,
M
is a non-negative integer that specifies the number of rotating GC log records per file. Each GC log record
corresponds to a GC event. A value of 0 specifies an unlimited number of GC log records per file.
N
is a non-negative integer that specifies the maximum number of rotating GC log files. A value of 0 specifies an
unlimited number of files.
You must use both M and N when you use the -XX:GCLogLimits=M,N option. If this option is not specified, the
default behavior is to write a single GC log file with unlimited size. When rotation is in effect, a sequence number
is appended to the GC filename (0 through N-1).(Examples of file names are: filename.0, filename.1, and
filename.2.
With log rotation, when the specified maximum number of files (N) is reached, logging cycles back to the first file
in the sequence (filename.0), thereby overwriting the old GC data with new data. If the maximum number of files
(N) is never reached, then no log rotation occurs.
For example,
To rotate between two log files, each with a maximum of 100,000 GC records, use:
-XX:GCLogLimits=100000,2
To maintain an unlimited number of smaller files, each with a maximum of 1,000 GC records, use:
-XX:GCLogLimits=1000,0