Version pool management in a multilevel secure multiversion transaction manager

The paper presents initial results of an ongoing project to develop an experimental prototype of a multilevel secure (MLS) database system (DBS) based upon a multiversion scheduling protocol. The purpose of the project is to explore design alternatives and demonstrate feasibility. The work focuses on the mechanisms needed to provide efficient access to multiple versions of data as required by the protocol. With this protocol, strictly dominating transactions are serialized before active dominated transactions to avoid contention. These dominating transactions require access to old snapshots. The purpose of this work is to characterize the storage and access cost associated with the approach. We describe a prototype featuring an untrusted version pool mechanism to study this question. An analytical model is developed to predict storage and search costs. The analytical model is validated through measurements made on the prototype