Minimizing System Contention

It’s not uncommon for Oracle DBAs to field calls about a user being locked or “blocked” in the database. Oracle’s locking behavior is extremely sophisticated and supports simultaneous use of the database by multiple users. However, on occasion, it’s possible for a user to block another user’s work, mostly because of flaws in application design. This chapter explains how Oracle handles locks and how to identify a session that’s blocking others.

An Oracle database can experience two main types of contention for resources. The first is contention for transaction locks on a table’s rows. The second type of contention ...

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