APPLIES TO:

SYMPTOMS

Not able to drop a database link after changing the global_name of the database

The newly added global_name has a domain name attached to it.

When trying to drop the database link after this change throws the following error

ORA-02024: database link not found

But database link is present and the query on user_db_links displays the value

SQL> select * from global_name;


GLOBAL_NAME
---------------------------------------------------------
DB10GR2

SQL> create database link l1 connect to scott identified by tiger;


Database link created.

SQL> select db_link from user_db_links;

DB_LINK
---------------------------------------------------------

ERROR at line 1:
ORA-02024: database link not found

Even if the global_name is changed back to the original value, the same errors
occurs.

CAUSE

Initially when a database is created without domain in the global name, null will used from domain as opposed to .world in earlier releases
Later on when the global_name is altered to contain the domain part also, this domain remains even when the global_name is altered back a name without domain name

Example :-

SQL> select * from global_name;

GLOBAL_NAME
---------------------------------------------------------
DB10GR2

SQL> alter database rename global_name to DB10GR2.WORLD;

Database altered.

SQL> select * from global_name;

GLOBAL_NAME
---------------------------------------------------------
DB10GR2.WORLD

SQL> alter database rename global_name to DB10GR2;

Database altered.

SQL> select * from global_name;

GLOBAL_NAME
---------------------------------------------------------
DB10GR2.WORLD

The only option left to correct this is to update the base table props$

SOLUTION

There are two solutions:

1. Update sys.link$ and rename the name column to make it match so that the command to drop public database link works.
1.1. Take a complete consistent backup of the database
1.2. Execute the following:

$sqlplus /nolog
connect / as sysdba

SQL> update props$ set value$ = ‘<globalname without domain>‘ where name =‘GLOBAL_DB_NAME‘;

SQL>commit;

1.3 Drop the database link:

1.3.1. Connect as the schema user that owns the DBLINK and try to drop it.

If you still get ORA-2024: database link not found , that means the domain name is in your cache and needs to be cleared.

1.3.2. Flush shared pool thrice and retry drop database link.

alter system flush SHARED_POOL;
alter system flush SHARED_POOL;
alter system flush SHARED_POOL;

1.3.3. If step b doesn‘t help, you need to bounce your database and try to drop the database link.

1.3.4. Once the database link is dropped, the global_name can be changed back to the desired name containing domain part using the alter database rename global_name statement

2. The second solution consists on deleting the database link directly from sys.link$:

2.1. Take a complete consistent backup of the database or use CTAS can be used to backup sys.link$:

$sqlplus /nolog
connect / as sysdba

SQL> create table backup_link$ as select * from sys.link$:

2.2. Delete the DBLINK as follows:

$sqlplus /nolog
connect / as sysdba

SQL> delete sys.link$ where name=‘db_link_name>‘;

SQL>commit;

2.3. Verify if the operaion s correctly proceeded:

select db_link, username, host from user_db_links;

Reference

Bug 3675157 - ORA-02024: CANNOT DROP DBLINK AFTER THE GLOBAL_NAME PARAMETER IS CHANGED.

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REFERENCES