Categories
sql

committing transaction

When and how do you commit a transaction?
SQL> insert into lsc_t(x) values(1); ... (1) not committed
SQL> commit; ... (1) committed

SQL> insert into lsc_t(x) values(2); ... (2) not committed
SQL> alter table lsc_t disable primary key; ... (2) committed

SQL> set autocommit ON
SQL> insert into lsc_t(x) values(3); ... (3) committed
SQL> set autocommit OFF

SQL> insert into lsc_t(x) values(4); ... (4) not committed
SQL> disc ... (4) committed

Row 1 is committed after the commit keyword.

Row 2 is implicitely committed after before the alter table ddl statement.

Row 3 is autocommitted. Autocommit exists in sqlplus, but is more often seen in stateless applications (for instance a web application).

Row 4 is committed after a successfull disconnection.

But what appends if you kill your current session?


SQL> insert into lsc_t(x) values (5);

1 row created.

SQL> !ps
PID TTY TIME CMD
13903 pts/33 0:00 ksh
22384 pts/33 0:00 sqlplus

SQL> !kill 22384
Terminated

The row 5 is not commited

Ref: Overview of Transaction Management

A transaction ends when any of the following occurs:
– A user issues a COMMIT or ROLLBACK statement without a SAVEPOINT clause.
– A user runs a DDL statement such as CREATE, DROP, RENAME, or ALTER (*).
If the current transaction contains any DML statements, Oracle Database
first commits the transaction, and then runs and commits the DDL statement
as a new, single statement transaction.
– A user disconnects from Oracle Database. The current transaction is committed.
– A user process terminates abnormally. The current transaction is rolled back.

(*) but not ALTER SESSION

Please read On Implicit Commit

By Laurent Schneider

Oracle Certified Master

5 replies on “committing transaction”

Hi Laurent

I would like to precise your statement about implicit commit when executing a DDL statement.

In fact Row 2 (from your example) is committed before the alter table statement is executed. If you execute a DDL statement, it is always surrounded with a pair of implicit commit statements.

More details can be found in an article from Tom Kyte http://www.dbazine.com/oracle/or-articles/kyte2 in the chapter DDL Locks.

Regards
Dani

Oh yes, thanks for pointing this out, the row is committed even if the ddl fails, madness!


SQL> insert into lsc_t(x) values (5);
--> (5) not committed

1 row created.

SQL> create table tttt(x number) tablespace system;
create table tttt(x number) tablespace system
*
ERROR at line 1:
ORA-01950: no privileges on tablespace 'SYSTEM'
--> (5) committed

Hi Laurent

Another way to commit:
exec dbms_stats.gather_table_stats(user,’T’);

The documentation of dbms_stats package says:
Most of the procedures in this package commit the current transaction, perform the operation, and then commit again.

So don’t gather stats on temporary tables (on commit delete rows) 🙂

Regards,
Stefan

[…] Link to the original site Tags: Autocommit, Current, Disconnection, Dml Statements, Nbsp Nbsp Nbsp Nbsp Nbsp, ORACLE BLOGS, Rollback, Sql Insert, Sqlplus, Transaction Management, Web Application […]

Leave a Reply

Your email address will not be published.