Designing an Optimized Transaction Committ Protocol

kernel called KODA. In Digital's database addition to other database products, VAX Rdb/VMS services, KODA provides the and VAX DBMS, share the transaction capabilities same database kernel and commit processing for called KODA. KODA uses these two products. a grouping mechanism to In this paper, we address commit many concurrent some of the issues relevant transactions together. to efficient commit This feature enables high processing. We begin by transaction rates in a explaining the importance transaction processing (TP) of commit processing in environment. Since group achieving high transaction commit processing affects throughput. Next, we the maximum throughput describe in detail the of the transaction current algorithm for group processing system, the commit used in KODA. We KODA group designed then describe and contrast and implemented several several new designs grouping algorithms and for performing a group studied their performance commit. Following these characteristics. discussions, we present Preliminary results our experimental results. indicate that it is And, finally, we discuss possible to achieve up the possible direction to a 66 percent improvement of future work and some in transaction throughput conclusions. No attempt by using more efficient is made to present formal grouping designs. analysis or exhaustive Introduction empirical results for commit processing; Digital has two generalrather, the focus is on purpose database products, an intuitive understanding Rdb/VMS software, which of the concepts and tradesupports the relational offs, along with some data model, and VAX DBMS empirical results that software, which supports support our conclusions. the CODASYL (Conference on Data Systems Languages) data model. Both products layer on top of a database Digital Technical Journal Vol. 3 No. 1 Winter 1991 1 Designing an Optimized Transaction Commit Protocol Commit Processing For the purpose of To follow a discussion analysis, it is useful of commit processing, two to divide a transaction basic terms must first processed by KODA into four be understood. We begin phases: the transaction this section by defining a start phase, the data transaction and the "moment manipulation phase, the of commit." logging phase, and the commit processing phase. A transaction is the Figure 1 illustrates the execution of one or phases of a transaction more statements that in time sequence. The access data managed by a first three phases are database system. Generally, collectively referred to as database management systems "the average transaction's guarantee that the effects CPU cost (excluding the of a transaction are cost of commit)" and the atomic, that is, either last phase (commit) as "the all updates performed cost of writing a group within the context of the commit buffer." [1] transaction are recorded in the database, or no updates are reflected in the database. The point at which a transaction's effects become durable is known as the "moment of commit." This concept is important because it allows database recovery to proceed in a predictable manner after a transaction failure. If a transaction terminates abnormally before it reaches the moment of commit, then it aborts. As a result, the database system performs transaction recovery, which removes all effects of the transaction. However, if the transaction has passed the moment of commit, recovery processing ensures that all changes made by the transaction are permanent.