check invalid database link

If one database link is invalid, you cannot select through it

SQL> select * from dual@z;
select * from dual@z
ERROR at line 1:
ORA-02019: connection description for remote database not found

However, there is no STATUS command in your user_db_links table that you could use. For this purpose, write a function.

create function status(db_link varchar2)
return varchar2 is
x number;
execute immediate 'select 1 from dual@"'||
'"' into x;
return 'OK';
when others then return sqlerrm;

select db_link, status(db_link) from user_db_links;
------- --------------------------------------------------
L1.EXAM ORA-01017: invalid username/password; logon denied
L2.EXAM ORA-12154: TNS:could not resolve the connect ident

5 thoughts on “check invalid database link

  1. Rick Wiggins (@tarpaw)

    I created a similar function (actually, an ASSERT_USABLE_DB_LINK procedure) but I try the EXECUTE IMMEDIATE query a second time if I get an initial error the first time. If the DB link connection was made and then connectivity to the remote DB is lost and then restored, the first error will dump the broken DB link connection and the second EXECUTE IMMEDIATE query will succeed and create a new, usable DB link connection. If I get an error the second time, the DB link is really invalid and the error is thrown.

  2. Raj Jamadagni

    I also run following to see where the link points to … “select ‘DB Link XXXX now points to ‘ || property_value from database_properties@XXXX where property_name in (‘GLOBAL_DB_NAME’);”

  3. Pingback: check invalid database link for the DBA – Laurent Schneider

  4. Raj Jamadagni

    @Laurent, yes that is a good too, originally I used it to find DB version as well (until we upgraded all to same level), so it is an old relic. the one you suggested seems simpler to code too, thanks.

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