Transaction isolation levels in OrientDB define the degree to which concurrent transactions are isolated from each other and determine the level of consistency and concurrency control enforced by the database. OrientDB supports multiple isolation levels, each offering a different balance between concurrency and data consistency. Here are the commonly supported transaction isolation levels in OrientDB:
Read Uncommitted :
* In the Read Uncommitted isolation level, transactions are not required to hold any locks on database objects during reads or writes.
* This is the lowest isolation level, where transactions can read uncommitted changes made by other transactions.
* Read Uncommitted isolation level provides the highest concurrency but sacrifices data consistency, as transactions may see uncommitted or partially committed data from other transactions.
Read Committed :
* In the Read Committed isolation level, transactions are required to hold read locks on database objects during reads to prevent dirty reads.
* Transactions at this isolation level can only read committed data, ensuring that they do not see uncommitted changes made by other transactions.
* Read Committed isolation level provides a higher level of data consistency compared to Read Uncommitted, but still allows for a significant degree of concurrency.
Repeatable Read :
* In the Repeatable Read isolation level, transactions are required to hold read locks on database objects for the duration of the transaction to prevent dirty reads and non-repeatable reads.
* Transactions at this isolation level are guaranteed to see a consistent snapshot of the database throughout the transaction, preventing changes made by other transactions from being visible.
* Repeatable Read isolation level provides a higher level of data consistency by preventing non-repeatable reads, but may lead to increased contention and reduced concurrency in highly concurrent environments.
Serializable :
* In the Serializable isolation level, transactions are fully isolated from each other, and each transaction appears to execute sequentially, as if it were the only transaction running.
* Transactions at this isolation level are serialized to prevent all types of concurrency anomalies, including dirty reads, non-repeatable reads, and phantom reads.
* Serializable isolation level provides the highest level of data consistency but may lead to reduced concurrency and increased contention in highly concurrent environments.
Users can specify the desired isolation level for transactions in OrientDB when starting a new transaction. By selecting an appropriate isolation level based on application requirements and concurrency constraints, users can achieve the desired balance between data consistency and concurrency control in their database transactions.
