Manage large data sets
FOR rec in SELECT * from tablenm LOOP
--perform processing steps
The SELECT operation runs first and caches its results in memory or as a temporary file on disk, depending upon the size of the result set. The procedure then applies the steps in the inner processing loop.
If the table (tablenm) is very large, such as a table with millions of rows or one with many thousands of large rows, the temporary file can be a huge file that uses the free disk space on the host. Use caution when your stored procedures process very large tables.