Enabling GC logging for a DataSource’s JVM

Caplin Support recommend enabling garbage collection (GC) logging for production Java virtual machines (JVMs). Garbage collection logs provide valuable information for tuning a JVM’s heap size and investigating performance and memory problems.

For a detailed reference on JVM logging options, see the java command reference (Java 8) and Unified JVM Logging (Java 11).

Enabling GC logging for a C DataSource

C DataSources include Liberator, Transformer, and the TREP Adapter.

The following examples show the jvm-options used to configure GC logging for versions of Java supported by Caplin Platform 7. Add the appropriate configuration below to your DataSource’s java.conf file:

Java 8
jvm-options -XX:+PrintGCDetails
jvm-options -XX:+PrintGCDateStamps
jvm-options -XX:+UseGCLogFileRotation
jvm-options -XX:NumberOfGCLogFiles=10
jvm-options -XX:GCLogFileSize=5M
jvm-options -XX:+PrintConcurrentLocks
jvm-options -XX:+PrintCommandLineFlags
jvm-options -XX:+HeapDumpOnOutOfMemoryError (1)
jvm-options -XX:HeapDumpPath=var
Java 11
jvm-options -Xlog:gc:file=var/gc-%p.log:tags,time,uptime,level:filecount=10,filesize=5M
jvm-options -XX:+HeapDumpOnOutOfMemoryError (1)
jvm-options -XX:HeapDumpPath=var
1 If the DataSource’s JVM runs out of memory, dump the JVM heap before terminating the JVM. A heap dump can provide valuable information to Caplin Support.

Enabling GC logging for a Java DataSource

Java DataSources include Caplin RET Adapter Toolkit, the Caplin Barracuda Adapter, and the Caplin Wallstreet Adapter.

To enable GC logging for a Java DataSource, add the appropriate command-line options below to the java command in the DataSource’s DataSource/bin/start-jar.sh script:

Java 8
-Xloggc:var/gc-%p.log -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=10 -XX:GCLogFileSize=5M -XX:+PrintConcurrentLocks -XX:+PrintCommandLineFlags -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=var
Java 11
-Xlog:gc:file=var/gc-%p.log:tags,time,uptime,level:filecount=10,filesize=5M -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=var

See also: