A model of nested transaction with fine granularity of concurrency control

Proposes a new model of nested transactions which achieves higher concurrency of transactions than the traditional model. Most of the previously proposed concurrency control algorithms for nested transactions were based on two-phase locking (2PL). In such algorithms, however, the concurrency of transactions is not so high. To achieve high concurrency, it was decided to apply serialization graph testing (SGT) to the concurrency control of nested transactions. However, in the traditional nested transactions model, the subtransactions don´t satisfy the ACID (atomicity, consistency, isolation and durability) properties. We designed our nested transaction model so that each subtransaction satisfies the ACID properties. We considered applying an SGT scheduling algorithm to our model. By scheduling subtransactions as independent transactions, high concurrency can be achieved. However, the usual SGT algorithm causes deadlocks in our model. To avoid these deadlocks, we modified the usual SGT algorithm