Isolation levels are most helpful part in transactions when you are dealing with deadlocks. Other way when READ COMMITED isolation level is not helpful for your transactions.
We can say we have 5 major isolation levels in sql server.
READ COMMITED: It's a default isolation level. Other transactions are not able to perform any DML operations on the source which is being used by your transaction. Best Example opening account. You are not able to do any transaction until you open your account.
READ UNCOMMITED: You can set your transaction to READ UNCOMMITED when Other transaction are using your source. There are maximum possibilities of Dirty read in this isolation level.
REPEATABLE READ: Other Transactions can only insert new record (Phantom rows) to your tables but not able to update that records which are used by your transaction. Next transaction has to wait until your transaction is got finished. Best Example for this is Airline reservation system.
SERIALIZABLE: No operations are allowed by other transactions while your transaction is running under this isolation level. One of example you can see in wire transfer between accounts.
SNAPSHOT: When your transaction starts it takes snapshot of your resource. For this feature you must have enabled your database with Snapshot Feature in SQL SERVER engine.
We can say we have 5 major isolation levels in sql server.
READ COMMITED: It's a default isolation level. Other transactions are not able to perform any DML operations on the source which is being used by your transaction. Best Example opening account. You are not able to do any transaction until you open your account.
READ UNCOMMITED: You can set your transaction to READ UNCOMMITED when Other transaction are using your source. There are maximum possibilities of Dirty read in this isolation level.
REPEATABLE READ: Other Transactions can only insert new record (Phantom rows) to your tables but not able to update that records which are used by your transaction. Next transaction has to wait until your transaction is got finished. Best Example for this is Airline reservation system.
SERIALIZABLE: No operations are allowed by other transactions while your transaction is running under this isolation level. One of example you can see in wire transfer between accounts.
SNAPSHOT: When your transaction starts it takes snapshot of your resource. For this feature you must have enabled your database with Snapshot Feature in SQL SERVER engine.
One more Type is included in SNAPSHOT feature is READ COMMITED SNAPSHOT.
READ COMMITED SNAPSHOT: It takes Snapshot of resource from last commited transactions.
There are Down for Snapshot because it requires storage for taking snapshot.
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