When dealing with large quantities of clauses, the use of persistent knowledge is inevitable, and indexing methods are essential to answer queries efficiently. We introduce PerKMan, a storage manager that uses G-trees and aims at efficient manipulation of large amount of persistent knowledge. PerKMan may be connected to Prolog systems that offer an external C language interface. As well as the fact that the storage manager allows different arguments of a predicate to share a common index dimension in a novel manner, it indexes rules and facts in the same manner. PerKMan handles compound terms efficiently and its data structures adapt their shape to large dynamic volumes of clauses, no matter what their distribution. The storage manager achieves fast clause retrieval and reasonable use of disk space.