Explain transactions and transaction modes in sql server?

A transaction is a set of dml operations which must be make perminent as a whole or must be undone as a whole

Sql server runs in following transaction modes.

1.Autocommit
2.Implicit transaction mode.
3.Explicit transaction mode.

AutoCommit: If sql server runs in autocommit mode then the transactionwill be started automatically when user submits dml command and transaction ends with commit automatically.
In Autocommit mode user cannot control transactions


Implicit Transaction mode : In this transaction starts automatically with any dml command but transaction ends with commit or rollback

Ex

updaet or sql statement--transaction starts
commit/rollback -- transaction ends

Explicit transaction mode : In explicit transaction mode the transaction starts with 'begin transaction' command and the transaction ends with 'commit transaction' or 'rollback transaction'

begin transaction
update statement
commit/rollback transaction


set implicit_transaction on --> it sets the implicit transaction mode on.