Oracle synonym randomly not viewable

Question

here's a tricky case on which 5 peoples including a DBA have been struggling on for days... I offer lifetime consideration to the one which will identify the root cause of the issue.

here it is:

Oracle Client: 10g Oracle Server: 11g

We have 2 schemas and 1 user:

SCHEMA1

SCHEMA2

USER

We have 1 table 'TOTO' which is defined in SCHEMA1 (SCHEMA1.TOTO) We have a private synonym of table 'TOTO', called 'TOTO' defined in SCHEMA2, created like this:

CREATE SYNONYM SCHEMA2.TOTO FOR SCHEMA1.TABLE1;

We have granted SELECT,UPDATE,DELETE,INSERT priviledges on "SCHEMA2.TOTO " (so on the synonym) to SCHEMA2 (so that any session ran from SCHEMA2 has access to the synonym table)

GRANT SELECT, UPDATE, DELETE, INSERT ON SCHEMA2.TOTO TO SCHEMA2;

Our application connects to the DB with USER, then directly switches to SCHEMA2:

ALTER SESSION SET CURRENT_SCHEMA=SCHEMA2;

Then after that, it tries to perform a select query on the synonym table WITHOUT prefixing the synonym name by SCHEMA1 (this is a constrain of the framework we use):

SELECT COL FROM TOTO;

Most of the times this query works successfully, which is what we expect since we have altered our session to SCHEMA2, by default that where the objects are looked.

But sometimes it fails, with an ORA-00942: table or view does not exist error.

I insist on the fact that between the time when it works and when it fails, nothing has changed, we've just restarted the application (which is of course re-connecting to the DB the same way at each startup). We've been investigated with a DBA monitoring all the events on USER,SCHEMA1,SCHEMA2 hoping to find an external process modifying the GRANTS on one of thoses, between a success and a failure, but nothing changes. Yet, at some point, randomnly we get the ORA-00942 error, then we restart the application several times and it's back again...

Would someone have an idea or any suggestion/hint that could lead us to identify what we're missing here?

Many thanks for your help!

Answer 1

The grant should go to USER, not to SCHEMA2:

GRANT SELECT, UPDATE, DELETE, INSERT ON schema1.toto TO userxy;

This should solve the problem. If it doesn't, can you please post the result of

SELECT * FROM all_objects WHERE object_name='TOTO';