How to Delete consumed persistent messages form database store (openjms.db)

Hello,
  Am using openjms-0.7.6.1 and am using queue's and the message are sent in
persistent delivery mode and am using openjms.db for database store.

Does anyone know if openjms has any inbuilt mechanism wherein the
successfully consumed persistent messages are removed from the openjms.db?
or do i have to write a code to read openjms and delete the consumed
messages?

At present even though my persistent messages are being consumed my
openjms.db size keeps increasing.

I have tried using ObjectAdapter O=new ObjectAdapter("openjms.db",50,50,50);
				O.purgeMessages();
however it gives an error saying cant get lock over openjms.db

I have also tried using DatabaseService.getAdapter().purgeMessages();but
null pointer

Fatal error: java.lang.NullPointerException
Exiting.....
java.lang.NullPointerException
        at
org.exolab.jms.persistence.DatabaseService.getAdapter(DatabaseService.java:1
30)


Thanks
Deepa





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