FOR READ ONLY Clause

Use the FOR READ ONLY keywords to specify that the Select cursor declared for the SELECT statement is a read-only cursor. A read-only cursor is a cursor that cannot modify data.

Normally, you do not need to include the FOR READ ONLY clause in a SELECT statement. SELECT is a read-only operation by definition, so the FOR READ ONLY clause is usually unnecessary. In certain circumstances, however, you must include the FOR READ ONLY keywords in a SELECT statement.

If you attempt to include both the FOR READ ONLY clause and the FOR UPDATE clause in the same SELECT statement, the SELECT statement fails. For information on declaring a read-only cursor for a SELECT statement that does not include a FOR READ ONLY clause, see DECLARE statement.

If you have used the High-Performance Loader (HPL) in express mode to load data into the tables of an ANSI-compliant database, and you have not yet performed a level-0 backup of this data, the database is in read-only mode. When the database is in read-only mode, the database server rejects any attempts by a Select cursor to access the data unless the SELECT or the DECLARE includes a FOR READ ONLY clause. This restriction remains in effect until the user has performed a level-0 backup of the data.

In an ANSI-compliant database, Select cursors are update cursors by default. An update cursor is a cursor that can be used to modify data. These update cursors are incompatible with the read-only mode of the database. For example, this SELECT statement against the customer_ansi table fails: 
EXEC SQL declare ansi_curs cursor for
   select * from customer_ansi;
The solution is to include the FOR READ ONLY clause in your Select cursors. The read-only cursor that this clause specifies is compatible with the read-only mode of the database. For example, the following SELECT FOR READ ONLY statement against the customer_ansi table succeeds: 
EXEC SQL declare ansi_read cursor for
   select * from customer_ansi for read only;

DB-Access executes all SELECT statements with Select cursors, so you must specify FOR READ ONLY in all queries that access data in a read-only ANSI-compliant database. The FOR READ ONLY clause causes DB-Access to declare the cursor for the SELECT statement as a read-only cursor.

For more information on level-0 backups, see your HCL OneDB™ Backup and Restore Guide. For more information on Select cursors, read-only cursors, and update cursors, see DECLARE statement.

For more information on the express mode of the HPL of HCL OneDB, see the HCL OneDB High-Performance Loader User's Guide.