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Oracle updating large tables

The third performs an update, and conditionally inserts the row if the update touches zero rows.The fourth inserts the row, then performs an update if the insert fails with a duplicate value on index exception.The data in a global temporary table is private, such that data inserted by a session can only be accessed by that session.The session-specific rows in a global temporary table can be preserved for the whole session, or just for the current transaction.

INSERT INTO my_temp_table VALUES (1, 'ONE'); SELECT COUNT(*) FROM my_temp_table; COUNT(*) ---------- 1 SQL CREATE GLOBAL TEMPORARY TABLE my_temp_table ( id NUMBER, description VARCHAR2(20) ) ON COMMIT PRESERVE ROWS; -- Insert and commit, then check contents of GTT.

Unfortunately, prior to Oracle 12c, all undo associated with DML against a GTT is written to the normal undo tablespace, which is itself protected by redo.

As a result, using a GTT reduces the amount of redo generation, but does not eliminate it.

INSERT INTO my_temp_table WITH data AS ( SELECT 1 AS id FROM dual CONNECT BY level If you've read the previous section, you will already know the relationship between global temporary tables and redo.

The data in a GTT is written to the temporary tablespace, which is not directly protected by redo, so using a GTT improves performance by reducing redo generation.

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tablespace_name, s.extent_management FROM user_tables t, user_tablespaces s WHERE t.tablespace_name = s.

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