Posted in database, Transaction isolation level

Transaction isolation levels

1 Read Uncommitted The user A start a query, then user B made some changes, A will see the changes have not been committed yet (dirty read)
2 Read committed The user A start a query, user B made some changes and commit. But A will not see the changes made by B.
3 Repeatable Read The user A will not see the changes made by B (insert/delete) read the snapshot established by the first read, so 2 queries executed, with 2 different results (phantom read).
4 Serializable All transactions are completely in isolation fashion, executed serially one after another (lock-based concurrency control).

In Oracle, Repeated Read level is not supported, but in MySQL default isolation level is repeated Read.

 

 

 

 

 

 

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