A non-two-phase locking protocol for global concurrency control in distributed heterogeneous database systems

A concurrency control method is proposed for global transactions in a distributed heterogeneous database system. This method is applicable when the database sites are interconnected in a rooted tree fashion. It guarantees deadlock freedom in addition to serializability. A general architecture of a heterogeneous system is given. The global transaction manager (GTM) decomposes the global transactions initiated at a site and the subtransactions received from other sites into smaller subtransactions, some of which are sent to the GTMs of the other sites, and those remaining, called g-local transactions, are to be executed by the local transaction manager (LTM) at that site. A concurrency control mechanism ensures serializability among: the local transactions (including the g-local transactions of the global ones) at each site, the global transactions and the global and local transactions together