Thank you to everyone who tried to help. This turned out to be an Oracle limitation:
APPLIES TO:
PL/SQL - Version 9.2.0.8 and later Information in this document
applies to any platform.
Checked for relevance on 01-Apr-2015
SYMPTOMS
A PL/SQL block fails with error: ORA-00980: synonym translation is no
longer valid, when selecting data from a remote database. The
following code demonstrates this issue:
On DB3 (create the table)
CONNECT u3/u3 DROP TABLE tab; CREATE TABLE tab(c1 number); INSERT
INTO tab VALUES (1); COMMIT;
On DB2 (create a synonym to the table on DB3)
CONNECT u2/u2 DROP DATABASE LINK dblink2; CREATE DATABASE LINK
dblink2 CONNECT TO u3 IDENTIFIED BY u3 USING 'EMT102U6'; SELECT *
FROM global_name@dblink2; DROP SYNONYM syn2; CREATE SYNONYM syn2
FOR tab@dblink2; SELECT * FROM syn2;
On DB1 (create a synonym to the synonym on DB2)
CONNECT u1/u1 DROP DATABASE LINK dblink1; CREATE DATABASE LINK
dblink1 CONNECT TO u2 IDENTIFIED BY u2 USING 'EMT102W6'; SELECT *
FROM global_name@dblink1; DROP SYNONYM syn1; CREATE SYNONYM syn1
FOR syn2@dblink1; SELECT c1 from syn1;
This works in SQL but fails when called from PL/SQL
DECLARE num NUMBER; BEGIN SELECT c1 INTO num FROM syn1; END;
/
ERROR at line 4: ORA-06550: line 4, column 3: PL/SQL: ORA-00980:
synonym translation is no longer valid ORA-06550: line 4, column 3:
PL/SQL: SQL Statement ignored
CAUSE
This issue was reported in Bug 2829591 QUERING FROM A PL/SQL
PROCEDURE IN 9I -> 8I-> 7.3.4, GETTING ORA-980. This bug was closed
as 'NOT A BUG' for the following reasons
PL/SQL cannot instruct middle database (DB2) to follow the database
link during the compilation phase. Therefore in order for this PL/SQL
block to compile and run, both database links dblink1 and dblink2
should be defined on the front end database - DB1. During runtime
database link dblink2 will be looked up in DB2 as expected.
SOLUTION
To implement the solution, please execute the following steps:
- Create a database link dblink2 on DB1 pointing to DB3
SQL> create database link dblink2 connect to u3 identified by u3 using
'EMT102U6';
- Create and compile the PL/SQL block on DB1.
CREATE DATABASE LINK dblink2 CONNECT TO u3 IDENTIFIED BY u3 USING
'EMT102U6';
SELECT * FROM global_name@dblink2; DECLARE num NUMBER; BEGIN
SELECT c1 INTO num FROM syn1; END; / PL/SQL procedure successfully
completed.
TIP: Another option is to use dyanmic SQL in the PL/SQL block as a
work around. When using dynamic SQL the database link is not resolved
at compile time but at runtime.