Problem with External predicate in VPD

Hello,

I am trying to restrict access to service providers in OTM based on remark qualifier.

I have created VPD and assigned it to a user role.

When I try to search service provider through UI using that role, I am getting error message saying: "java.sql.SQLException: ORA-28113: policy predicate has error"

Below is the External Predicate:

SELECT 'x' FROM SERVPROV sp, LOCATION l, LOCATION_REMARK lr WHERE lr.remark_qual_gid='IS_ACTIVE' AND lr.remark_text='Yes' AND sp.SERVPROV_GID=lr.location_gid AND lr.location_gid=l.location_gid

Can any one help me on this??