calcengine worker does not start

[pewi]

hi all,
if I try top open calc application in ox appsuite, I'm getting an "error occured" message.

These are the error messages in the log file:
----->----
2015-06-11T13:00:47,851+0200 INFO [Thread-38567] com.openexchange.office.calcengine.client.impl.Cal cEngineWorkerLogSink.impl_log(CalcEngineWorkerLogS ink.java:172)
define memory limit : 3145728 KB ...

2015-06-11T13:00:47,963+0200 ERROR [Thread-38568] com.openexchange.office.calcengine.client.impl.Cal cEngineWorkerLogSink.impl_log(CalcEngineWorkerLogS ink.java:166)
Could not create the Java virtual machine.

2015-06-11T13:00:47,963+0200 INFO [Thread-38567] com.openexchange.office.calcengine.client.impl.Cal cEngineWorkerLogSink.impl_log(CalcEngineWorkerLogS ink.java:172)
Error occurred during initialization of VM

2015-06-11T13:00:47,963+0200 INFO [Thread-38567] com.openexchange.office.calcengine.client.impl.Cal cEngineWorkerLogSink.impl_log(CalcEngineWorkerLogS ink.java:172)
Could not reserve enough space for object heap

2015-06-11T13:01:06,857+0200 ERROR [message-handler-0] com.openexchange.office.tools.jobpool.JobBase.acti vateJob(JobBase.java:76)
Worker not started in time.
-----<----

The config file "/opt/open-xchange/etc/ox-scriptconf.sh" looks like this:
..
# Defines the Java options for the groupware Java virtual machine.
JAVA_XTRAOPTS="-Dsun.net.inetaddr.ttl=3600 -Dnetworkaddress.cache.ttl=3600 -Dnetworkaddress.cache.negative.ttl=10 -Dlogback.threadlocal.put.duplicate=false -server -Djava.awt.headless=true -Xmx2048M -XX:MaxPermSize=256m -XX:+UseConcMarkSweepGC -XX:+UseParNewGC -XX:CMSInitiatingOccupancyFraction=75 -XX:+UseCMSInitiatingOccupancyOnly -XX:NewRatio=3 -XX:+UseTLAB -XX:+DisableExplicitGC -Dosgi.compatibility.bootdelegation=false -XX:-OmitStackTraceInFastThrow"

# Defines the Java options for all command line tools. CLTs need much less memory compared to the groupware process.
JAVA_OXCMD_OPTS="-Djava.net.preferIPv4Stack=true"
..

Environment is:
Version der Benutzeroberfläche: 7.6.2 Rev17
Server-Version: 7.6.2-Rev18
Runnning on Debian 7 64bit with 12Gb RAM


Is there a way to increase the heap size?

Thanks for any help!
Regards Peter