Schema Object Dependencies

Some schema objects refer to other objects, creating a schema object dependency.

For example, a view contains a query that references tables or views, while a PL/SQL subprogram invokes other subprograms. If the definition of object A references object B, then A is a dependent object on B, and B is a referenced object for A.

infrastructure services

Oracle Database provides an automatic mechanism to ensure that a dependent object is always up to date with respect to its referenced objects. When you create a dependent object, the database tracks dependencies between the dependent object and its referenced objects. When a referenced object changes in a way that might affect a dependent object, the database marks the dependent object invalid. For example, if a user drops a table, no view based on the dropped table is usable.

it consulting

An invalid dependent object must be recompiled against the new definition of a referenced object before the dependent object is usable. Recompilation occurs automatically when the invalid dependent object is referenced.

it support

As an illustration of how schema objects can create dependencies, the following sample script creates a table test_table and then a procedure that queries this table:

CopyCREATE TABLE test_table ( col1 INTEGER, col2 INTEGER );

CREATE OR REPLACE PROCEDURE test_proc
AS
BEGIN
 FOR x IN ( SELECT col1, col2 FROM test_table )
 LOOP
   -- process data
   NULL;
 END LOOP;
END;
/

The following query of the status of procedure test_proc shows that it is valid:

CopySQL> SELECT OBJECT_NAME, STATUS FROM USER_OBJECTS WHERE OBJECT_NAME = 'TEST_PROC';
 
OBJECT_NAME STATUS
----------- -------
TEST_PROC   VALID

After adding the col3 column to test_table, the procedure is still valid because the procedure has no dependencies on this column:

CopySQL> ALTER TABLE test_table ADD col3 NUMBER;
 
Table altered.
 
SQL> SELECT OBJECT_NAME, STATUS FROM USER_OBJECTS WHERE OBJECT_NAME = 'TEST_PROC';
 
OBJECT_NAME STATUS
----------- -------
TEST_PROC   VALID

However, changing the data type of the col1 column, which the test_proc procedure depends on in, invalidates the procedure:

CopySQL> ALTER TABLE test_table MODIFY col1 VARCHAR2(20);
 
Table altered.
 
SQL> SELECT OBJECT_NAME, STATUS FROM USER_OBJECTS WHERE OBJECT_NAME = 'TEST_PROC';
 
OBJECT_NAME STATUS
----------- -------
TEST_PROC   INVALID

Running or recompiling the procedure makes it valid again, as shown in the following example:

CopySQL> EXECUTE test_proc
 
PL/SQL procedure successfully completed.
 
SQL> SELECT OBJECT_NAME, STATUS FROM USER_OBJECTS WHERE OBJECT_NAME = 'TEST_PROC';
 
OBJECT_NAME STATUS
----------- -------
TEST_PROC   VALID

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