RENAME TABLE in a table maintenance scenario

The RENAME TABLE statement is useful when you need to temporarily take a table offline for maintenance that involves structural changes to the table. Applications can continue to run against another copy of the table until maintenance is complete.

One way of accomplishing this is refer to the name of the table as an unqualified name in all applications. The unqualified table name is implicitly qualified by the content of the CURRENT SCHEMA special register. You set CURRENT SCHEMA to the schema of the real table to cause applications to access the real table. Before you take the real table offline, you change the CURRENT SCHEMA special register to the name of the schema for the alternate copy of the table. When all applications are running with the alternate copy of the table, the real table can be modified. An example of such a modification is adding a column to the table.

Later, when table maintenance is complete, you can set the CURRENT SCHEMA special register to the name of the schema for the real table to cause all applications to switch back to using the real table.