Access Modes

Access modes affect read and write concurrency for rows within transactions. Use access modes to control data modification. SET TRANSACTION can specify that a transaction is read-only or read-write. By default, transactions are read-write. When you specify a read-only transaction, certain limitations apply. Read-only transactions cannot perform the following actions:

• Insert, delete, or update rows of a table.
• Create, alter, or drop any database object such as schemas, tables, temporary tables, indexes, or SPL routines.
• Grant or revoke access privileges.
• Update statistics.
• Rename columns or tables.

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