ORA-04062 signature of package has been changed solution and commands

The error ORA-04062: signature of package has been changed occurs in Oracle when a PL/SQL package (or package body) has been modified (such as by recompilation or alteration) since it was last used by a session. The session that encounters the error has a "stale" version of the package in its memory, which is inconsistent with the latest version in the database.

To resolve the ORA-04062 error, you can try the following steps

Solution 1: 

Reconnect the session

Sometimes, simply disconnecting and reconnecting the session will resolve the issue, as it forces the session to reload the latest version of the package.

Command:

ALTER SESSION CLOSE DATABASE LINK <link_name>;

Then reconnect.

Solution 2: 

Recompile the package

You can explicitly recompile the package (or the package body) to ensure it is valid and consistent in the database.

Command:

ALTER PACKAGE <package_name> COMPILE;

ALTER PACKAGE <package_name> COMPILE BODY;

This will recompile the package and the body, ensuring that the signatures are consistent.

Solution 3: 

Flush the shared pool

If multiple sessions are using an outdated version of the package, flushing the shared pool may help force Oracle to reload the package's latest version.

Command:

ALTER SYSTEM FLUSH SHARED_POOL;

This will clear all the cached objects in the shared pool, including the outdated package.

Solution 4: 

Use DBMS_SESSION to reset package state

If you cannot disconnect the session or flush the shared pool, you can use the

 DBMS_SESSION.RESET_PACKAGE procedure to reset the state of PL/SQL packages within the session.

Command:

EXEC DBMS_SESSION.RESET_PACKAGE;

This resets the package state for the session and should allow the session to use the latest version of the package.

These steps should help resolve the ORA-04062 error by ensuring that your session or instance uses the correct version of the package.