### 15.21.5 InnoDB Error Handling

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 The following items describe how `InnoDB` performs error handling. `InnoDB` sometimes rolls back only the statement that failed, other times it rolls back the entire transaction.

* If you run out of file space in a [tablespace](glossary.html#glos_tablespace), a MySQL `Table is full` error occurs and `InnoDB` rolls back the SQL statement.

* A transaction [deadlock](glossary.html#glos_deadlock) causes `InnoDB` to [roll back](glossary.html#glos_rollback) the entire [transaction](glossary.html#glos_transaction). Retry the entire transaction when this happens.

   A lock wait timeout causes `InnoDB` to roll back the current statement (the statement that was waiting for the lock and encountered the timeout). To have the entire transaction roll back, start the server with [`--innodb-rollback-on-timeout`](innodb-parameters.html#sysvar_innodb_rollback_on_timeout) enabled. Retry the statement if using the default behavior, or the entire transaction if [`--innodb-rollback-on-timeout`](innodb-parameters.html#sysvar_innodb_rollback_on_timeout) is enabled.

   Both deadlocks and lock wait timeouts are normal on busy servers and it is necessary for applications to be aware that they may happen and handle them by retrying. You can make them less likely by doing as little work as possible between the first change to data during a transaction and the commit, so the locks are held for the shortest possible time and for the smallest possible number of rows. Sometimes splitting work between different transactions may be practical and helpful.

* A duplicate-key error rolls back the SQL statement, if you have not specified the `IGNORE` option in your statement.

* A `row too long error` rolls back the SQL statement.

* Other errors are mostly detected by the MySQL layer of code (above the `InnoDB` storage engine level), and they roll back the corresponding SQL statement. Locks are not released in a rollback of a single SQL statement.

 During implicit rollbacks, as well as during the execution of an explicit [`ROLLBACK`](commit.html) SQL statement, [`SHOW PROCESSLIST`](show-processlist.html) displays `Rolling back` in the `State` column for the relevant connection.

