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The transaction isolation level is a state within databases that specifies the amount of data that is visible to a statement in a transaction, specifically when the same data source is accessed by multiple transactions simultaneously.
Transaction isolation level is part of the isolation state of a database management system. Isolation is one of the ACID (atomicity, consistency, isolation, durability) properties.
Techopedia Explains Transaction Isolation Level
The transaction isolation level is primarily used as a means to provide accurate and reliable access to data within concurrent transactions. For example, two different transactions might be accessing the same data simultaneously. Therefore, if the change made on the data by one transaction is not passed to the other transaction, it can affect database operations. To circumvent this, DBMS employs different transaction isolation levels that enforce read and write locks on the data. There are four different types of transaction isolation levels.
- Serializable: Implements read and writes locks until the transaction is finished. Also implements range locks.
- Repeatable Reads: Implements read and write locks until the transaction is completed. Doesn’t manage range locks.
- Read Committed: Implements write locks until the transaction is completed but releases read locks when a SELECT operation is performed.
- Read Uncommitted: One transaction can see the uncommitted changes made by the other transaction
