Design, implementation and performance study of reliable transactions in X.500 directory service

Replication of Directory information improves system performance and availa bility. This is provided in 1993 Standard through a shadowing mechanism. Ho wever, the standard specifies only weak consistency requirement. This is no t satisfactory as some applications may require strong consistency with ato mic (all-or-none) updates. This article describes the effort to incorporate the transaction function into the Directory in order to support the strong consistency requirement. An object-objected approach is used to design and implement the system. Appropriate object models for the DUA and the DSA ar e developed to include the transaction capability. The atomic update is ens ured by the transaction manager, which controls and coordinates the distrib uted transaction and the CCR ASE, which tracks and transfers the atomic tra nsaction messages on single transaction branch. This is assisted by a resou rce manager consisting of a local database with appropriate APIs and the un derlying database manager which, ensures the ACID properties of the atomic updates. Performance evaluation of the system implemented indicates a trans action overhead of 31% for commit case and 14% for rollback case. The bottl eneck areas include the local database access, the network processing overh ead and the size of replicas. The overheads can be reduced by employing adv anced hardware and software. Thus, the usefulness of transaction capability outweighs the overhead consideration. (C) 1999 Elsevier Science B.V. All r ights reserved.