Commit protocols for externalized-commit heterogeneous database systems

Abstract

Abstract. In designing a heterogeneous database systems, one of the main technical challenges is developing techniques for ensuring global commit. That is, guaranteeing that a transaction spanning multiple individual database management systems (DBMSs) either commits at all the participating DBMSs or at none of them. Previous work in this area typically assumes that the participating DBMSs do not provide a mechanism for interacting with their commit facilities. While this is true in many cases, in practice there are systems which support a programmatic interface to their commit protocols. We refer to database systems offering such facilities as externalized commit DBMSs.The focus of this paper is on commit protocols for these systems. We propose two new commit protocols for externalized commit DBMSs. The first may be used to obtain global commit in heterogeneous database systems composed of DBMSs with different 2-phase commit protocols (e.g., centralized and linear). The second protocol is more general, and ensures global commit even if the participating DBMSs employ 3-phase commit protocols. The more general protocol also preserves database autonomy, since it does not block a DBMS upon failure of another system. We describe both protocols in detail and prove their correctness.