Abstract: A method and apparatus for creating a transitive closure of a database when the database is stored on a secondary storage in the form of links connecting nodes. The method consists of partitioning the database, transferring one partition at a time from the secondary storage to the main memory, and processing a partition in such a way that accesses to the portions of the database not in main memory are minimized. As much of the unprocessed database as would fit a predetermined fraction of main memory is fetched as one partition, and if, during the processing of this partition, the main memory becomes full, the size of the partition is reduced dynamically by discarding a portion of the database in the current partition, and including this portion in the next partition. The processing of a partition involves, for each node in the partition, the operation of creating a direct connection between every pair of nodes that are indirectly connected through this node.