OPJ Tutorial: Storage Management

In the current OPJ prototype, primary memory storage management is managed exactly as in the standard Java platform.  Secondary storage management, sometimes referred to as persistent store garbage collection, is not automatic and must take place offline.It is managed by a special tool, opjgc.

As modifications are made to objects in an OPJ system, garbage will eventually accrue in the persistent store. Eventually, the persistent store can run out of space, just as the primary memory manager can run out of primary memory,  requiring a garbage collection. In OPJ this would manifest itself as a checkpoint exception. At that point, it would be necessary to shut down the application, run opjgc and then resume the application.

Another reason for running opjgc periodically is to minimize fragmentation in the persistent store as this can affect application performance due to the increased data traffic.