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What are different Transaction Isolation levels in JDBC? Transaction Isolation levels are used to implement locking. They decide how one process is isolated from the other. We have four Transaction Isolation Levels
1. Read Committed
- No two transactions can change the data at the same time. The shared lock is held for the record for the duration of the transaction and no other transaction can access the record.
2. Read Uncommitted
- This allows least restrictions to the record, meaning no shared locks and no exclusive locks. This kind offers best data concurrency but threat to data integrity.
3. Read Table Read
- This level allows new rows that can be inserted in the table and can even be read by the transactions.
4. Serializable
- This applies most restrictive setting holding shared locks on the range of data. Explain the different Transaction Isolation levels in JDBC. The transaction levels specifies the data that is visible to the statements within a transaction.
The following are the transaction isolation levels :
1. JDBC_TRANSACTION_NONE
This constant allows JDBC driver not to support transactions.
2. JDBC_TRANSACTION_READ_UNCOMMITTED
In this level, the transaction is allowed to perform uncommitted changes to the data in the database. This level allows to use all database anomalies.
3. JDBC_TRANSACTION_READ_COMMITTED
In this level, the changes made within a transaction are not reflected until the transaction is committed. Dirty reads are prevented with this level.
4. JDBC_TRANSACTION_REPEATABLE_READ
The read rows retains locks in order not to change them by another transactions at the time of transaction incompletion. This level disallows nonrepeatable reads and dirty reads. It is possible to perform phantom read actions.
5. JDBC_TRANSACTION_SERIALIZABLE
This level locks the transactions. With this action, the conditions followed by where clause cannot be changed by other truncations which adds values or removes values from a table. All database anomalies are prevented by this level. Different types of Transaction Isolation Levels. Transaction Isolation levels specifies the visible data to statements within a single transaction. These levels directly impact the various levels of the concurrent access.
Transaction isolation levels
There are five levels of transaction isolation which are as follows:
1. JDBC_TRANSACTION_NONE: A special constant that JDBC driver does not support transactions.
2. JDBC_TRANSACTION_READ_UNCOMMITTED: Allows looking after the uncommitted changes to the database.
3. JDBC_TRANSACTION_READ_COMMITTED: The transactions are externally invisible until the transaction is committed. The dirty reads prevention is possible with this level.
4. JDBC_TRANSACTION_REPEATABLE_READ: The readable rows retain locks by which another transaction can not change them until the transaction completes. It disallows dirty reads and non repeatable reads.
5. JDBC_TRANSACTION_SERIALIZABLE: The tables are locked for the transaction which makes the WHERE conditions not to be changed by other transactions. This process prevents all database anomalies.
To change the transaction levels, the setTransactionIsolation() method is utilized.
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