This paper presents work currently in progress on Disk Garbage Collection issues for PJava, an orthogonally persistent version of Java. In particular, it concentrates on the initial Prototype of the Disk Garbage Collector of PJava0 which has already been implemented. This Prototype was designed to be very simple and modular in order to be easily changed, evolved, improved, and allow experimentation. Several experiments were performed in order to test possible optimisations; these experiments concentrated on the following four areas: a) efficient access to the store; b) page-replacement algorithms; c) efficient discovery of live objects during compaction; and d) dealing with forward references. The paper presents a description of the Prototype's architecture, the results of these experiments and related discussion, and some future directions based on the experience gained from this work.