Question

explain the concept of AUTOCOMMIT
Also, discuss when does the AUTOCOMMIT is set to OFF automatically explain with the help of examples​

Answer 1

In the context of data management, autocommit is a mode of operation of a database connection. Each individual database interaction (i.e., each SQL statement) submitted through the database connection in autocommit mode will be executed in its own transaction that is implicitly committed. A SQL statement executed in autocommit mode cannot be rolled back.

Autocommit mode, in theory, incurs per-statement transaction overhead, having often undesirable performance or resource utilization impact. Nonetheless, in systems such as Microsoft SQL Server, as well as connection technologies such as ODBC and Microsoft OLE DB, autocommit mode is the default for all statements that change data, in order to ensure that individual statements will conform to the ACID (atomicity-consistency-isolation-durability) properties of transactions.[1]

The alternative to autocommit mode (non-autocommit) means that the SQL client application itself is responsible for issuing transaction initiation (start transaction) and termination (commit or rollback) commands. Non-autocommit mode enables grouping of multiple data manipulation SQL commands into a single atomic transaction.

Most DBMS (e.g. MariaDB[2]) force autocommit for every DDL statement even in non-autocommit mode. Before DDL statement starts previous DML statements in transaction are (auto)committed. Each DDL is executed in own new autocommit transaction. For following DDL statements new transaction is automatically started if needed.

Answer 2

When you write an SQL statement in SQL Developer, you perform an operation on that data. If you’re just reading the data, this is pretty straightforward.

Where it acts differently is when you change data in the database. This is usually done with the DELETE, INSERT, or UPDATE statements.

If you run an SQL statement that does any of these functions, then the data will be updated, but it won’t be committed.

If you’re not sure what committed means (when we talk about databases), it just means that the data is not permanently saved. It allows you to see the changes in your session, and then you can make a conscious decision to update the changes permanently (committing) or undoing the changes (rolling back).

Now, this is the default behaviour. There are two separate steps to this – running the statement to change the data, and then a second command to commit the changes to the database.

SQL Developer allows you to change this default behaviour, so that the statement is run and the changes are saved in a single step – hence the term “auto commit”.