Enhanced Data Locking to Serve ACID Transaction Properties in the Oracle Database

Relational databases are characterized by precise data models, formed by the entities and relationships. Integrity and consistency are maintained by the transactions, which ensure transfer from one consistent state to another. Consistency is ensured at the latest at the end of the transaction itself. SQL norm specifies two lock types applied on the data row level to serve the consistency in the parallel data access. However, Oracle Database uses a different approach relying on the transaction logs to provide historical consistent data images. In this paper, Reservable attributes are discussed, introduced in Oracle 23c version by focusing on the performance, limitations and general issues.