Transaction Logging

A database or table is said to have or use transaction logging when SQL data manipulation statements in a database generate logical-log records.

The database-logging status indicates whether a database uses transaction logging. The log-buffering mode indicates whether a database uses buffered or unbuffered logging, or ANSI-compliant logging. For more information, see Database-Logging Status and Managing Database-Logging Status.

In Extended Parallel Server, databases always use transaction logging. If you do not specify the buffering mode for a database, the default is unbuffered logging. You can use the SQL statement SET LOG or the ondblog utility to change the log-buffering mode. For information on ondblog, see the chapter on utilities in the IBM Informix: Administrator's Reference.

Although databases are always logged, you can use logging or nonlogging tables within a database. The user who creates the table specifies the type of table. Even if you use nonlogging tables, the database server always logs some events. For more information, see Logging and Nonlogging Tables.

Transactions against multiple coservers are always unbuffered. If any regular table or fragment involved in a transaction resides on a coserver other than the connection coserver for the application that makes the request, the database server uses unbuffered logging for that transaction. If all tables involved in the transaction are raw tables, no buffering takes place.

For local transactions, you can specify either buffered or unbuffered logging. (Local transactions are operations on the same coserver, including connection to applications). The table type determines the log-buffering mode for local transactions on one coserver.