PostgreSQL provides various lock modes to control concurrent access to data in tables. These modes can be used for application-controlled locking

PostgreSQL provides a rich set of tools for developers to manage concurrent access to data. Internally, data consistency is maintained by using

The SQL standard defines four levels of transaction isolation. The most strict is Serializable, which is defined by the standard in a paragraph

It is very difficult to enforce business rules regarding data integrity using Read Committed transactions because the view of the data is shifting with each statement, and

Though PostgreSQL provides nonblocking read/write access to table data, nonblocking read/write access is not currently offered for every index

Some DDL commands, currently only TRUNCATE and the table-rewriting forms of