Partition Selection Policies in Object Database Garbage

The automatic reclamation of storage for unreferenced objects is very important in object databases. Existing language system algorithms for automatic storage reclamation have been shown to be inappropriate. In this paper , we investigate methods to improve the performance of algorithms for automatic storage reclamation of object databases. These algorithms are based on a technique called partitioned garbage collection, in which a subset of the entire database is collected independently of the rest. Speciically, we investigate the policy that is used to select what partition in the database should be collected. The policies that we propose and investigate are based on the intuition that the values of overwritten pointers provide good hints about where to nd garbage. Using trace-driven simulation, we show that one of our policies requires less I/O to collect more garbage than any existing implementable policy and performs close to a near-optimal policy over a wide range of database sizes and object connectivities.