On implicit commit

An explicit commit is when you issue a COMMIT statement

SQL> create table t(x number);

Table created.

SQL> insert into t values(1);

1 row created.

SQL> commit;

Commit complete.

An implicit commit is when a commit is issued without your approval.

ex: AUTOCOMMIT (default is OFF)
SQL> set autoc on
SQL> insert into t values(1);

1 row created.

Commit complete.

ex: EXITCOMMIT (default is ON)
SQL> set autoc off exitc on
SQL> truncate table t;

Table truncated.

SQL> insert into t values(1);

1 row created.

SQL> disc
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> conn scott/tiger
Connected.
SQL> select * from t;
X
----------
1

before / after a successful DDL statement
SQL> truncate table t;

Table truncated.

SQL> insert into t values(1);

1 row created.

SQL> create index i on t(x);

Index created.

SQL> rollback;

Rollback complete.

SQL> select * from t;
X
----------
1

Before / after an unsuccessful DDL statement, sometimes :
SQL> truncate table t;

Table truncated.

SQL> insert into t values(1);

1 row created.

SQL> create index i on t(blabla);
create index i on t(blabla)
*
ERROR at line 1:
ORA-00904: "BLABLA": invalid identifier

SQL> rollback;

Rollback complete.

SQL> select * from t;
X
----------
1

But not always :
SQL> truncate table t;

Table truncated.

SQL> insert into t values(1);

1 row created.

SQL> create index i on t();
create index i on t()
*
ERROR at line 1:
ORA-00936: missing expression

SQL> rollback;

Rollback complete.

SQL> select * from t;

no rows selected

In the last case, no DDL was executed, but in the case before that, the DDL was executed and failed.

If you want to commit, use COMMIT 🙂

4 thoughts on “On implicit commit”

  1. Pingback: Laurent Schneider » committing transaction

  3. Gokhan Atil

    Hi, it’s an interesting article!

    “Before/after an unsuccessful DDL statement, sometimes, but not always” – In my humble opinion, it’s about which phase of parsing you get the error.

    If you get the error in “Translation and verification” phase (aka syntax check), there won’t be an implicit commit (i.e. ora-907, ora-904, ora-972).

    If parser goes to next phase (semantic check), there will be an implicit commit even parsing (and DDL) is unsuccessful.

    Regards

    Gokhan

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