Controlling Data Modification with Access Modes

Informix database servers support access modes. Access modes affect read and write concurrency for rows within transactions and are set with the SET TRANSACTION statement. You can use access modes to control data modification among shared files.

Transactions are read-write by default. If you specify that a transaction is read-only, that transaction cannot perform the following tasks:

• Insert, delete, or update table rows
• Create, alter, or drop any database object such as a schema, table, temporary table, index, or stored routine
• Grant or revoke privileges
• Update statistics
• Rename columns or tables

Read-only access mode prohibits updates.

You can execute stored routines in a read-only transaction as long as the routine does not try to perform any restricted statements.

For information about how to use the SET TRANSACTION statement to specify an access mode, see the IBM Informix: Guide to SQL Syntax.