Efficient Incremental Garbage Collection for Client-Server Object Database Systems

We describe an eficient server-based algorithm for garbage collecting object-oriented databases in a client/server environment. The algorithm is incremental and runs concurrently with client transactions. Unlike previous algorithms, it does not hold any locks on data and does not require callbacks to clients. It is fault tolerant, but performs very little logging. The algorithm has been designed to be integrated into existing OODB systems, and therefore it works with standard implementation techniques such as two-phase locking and writeahead-logging. In addition, it supports client-server performance optimizations such as client caching and flexible management of client buffers. We describe an implementation of the algorithm in the EXODUS storage manager and present results from an initial performance study.