Strange error in query executed via DBLink

Question

Hi,
I am running below big query(existing code in my project) on a oracle database(DB1) schema which accesses data from tables located in a remote oracle database(DB2) schema.
But I am getting error:
ORA-00904: "CERMA"."EFFECTIVE_TO": invalid identifier
ORA-02063: preceding line from <DB_LINK_NAME>
The concerned table is present in remote database  and  simple "select *  from" on the concerned table from  DB1 is working properly but when used in below query it is giving the above error.
The system design is as follows:
DB2  -  In this database ,Views are created in SCHEMA1 of this database which refer the underlying tables in SCHEMA2 of same database.
e.g. view name = clm_claims_basic_info_vw
DB1  -  In this database , synonyms are created(with name same as underlying tables) to access the underlying table data via the views created in DB2.
e.g. synonym name = clm_claims_basic_info
DB1  -  Query executed in this database which uses all the synonyms.
e.g.
select ..... from clm_claims_basic_info,clm_claim_scheme_dtl
Also this query was working fine few days back and now suddenly failing without any code-changes, but we don't know what else has changed.
Can you please suggest what could be the reason?
SELECT ccbi.claim_number claim_no, npm.policy_no policy_no,
     cgm.group_no company_ref_no, cgm.NAME company_name
    FROM clm_claims_basic_info ccbi,
     nbs_policy_mst npm,
     com_group_mst cgm,
     com_product_mst cpm,
     clm_member_dtl cmd,
     clm_assessment ca,
     clm_claim_scheme_dtl ccsd,
     clm_plan_dtl cpd,
     (SELECT mem_escal.member_escalation_type_vid,
                mem_escal.member_max_escal_rate,
                mem_escal.member_min_escal_rate,
                mem_escal.member_escal_rate,
                mem_escal.claim_basic_info_id,
                mem_escal.member_esclation_basis_vid,
                add_escal.additional_escalation_type_vid,
                add_escal.additional_max_escal_rate,
                add_escal.additional_min_escal_rate,
                add_escal.additional_escal_rate,
                add_escal.additional_esclation_basis_vid,
                mem_escal.first_escal_dt, mem_escal.escal_dt
         FROM (SELECT cerm.escalation_type_vid
                                                    member_escalation_type_vid,
                          cerm.max_escal_rate member_max_escal_rate,
                          cerm.min_escal_rate member_min_escal_rate,
                          cerm.escalation_rate member_escal_rate,
                          ccbi.claims_basic_info_id claim_basic_info_id,
                          cerm.escalation_basis_vid
                                                    member_esclation_basis_vid,
                          mi_claims_pkg.clm_get_escalation_date_fnc
                              (ccbi.claims_basic_info_id,
                                cpd.escal_applies_to_vid,
                                1,
                                cpd.escal_applies_to_day,
                                cpd.escal_applies_to_month_vid,
                                ccbi.event_dt,
                                ccbi.clm_acceptance_dt
                              ) first_escal_dt,
                          NULL escal_dt
                    FROM clm_claims_basic_info ccbi,
                          clm_claim_scheme_dtl ccsd,
                          clm_plan_dtl cpd,
                          clm_escalation_dtl cede,
                          com_escalation_rate_mst cerm
                  WHERE ccbi.claims_basic_info_id =
                                                        ccsd.claim_basic_info_id
                     AND ccsd.plan_id = cpd.plan_id
                     AND cede.claim_basic_info_id(+) =
                                                      ccbi.claims_basic_info_id
                     AND cede.escal_dt IS NULL
                     AND cpd.is_escal_apply_id = 'Y'
                     AND ccbi.product_id = 4
                     AND cerm.product_id = ccbi.product_id
                     AND cerm.escalation_basis_vid =
                                                      cpd.escal_memben_rate_vid
                     AND (   (    ccbi.claim_status_vid = 2880
                                 AND ccbi.event_dt
                                          BETWEEN cerm.effective_from
                                                AND NVL (cerm.effective_to,
                                                            TO_DATE ('31122999',
                                                                        'DDMMYYYY'
                            OR (    ccbi.claim_status_vid != 2880
                                 AND cede.first_escal_dt
                                          BETWEEN cerm.effective_from
                                                AND NVL (cerm.effective_to,
                                                            TO_DATE ('31122999',
                                                                        'DDMMYYYY'
                     AND (   (    cpd.escal_memben_rate_vid = 2334
                                 AND cpd.escal_memben_perc =
                                                             cerm.escalation_rate
                            OR (    cerm.escalation_type_vid IN
                                                              (3962, 3963, 4442)
                                 AND cerm.escalation_value_by_vid = 4299
                            OR (    cpd.escal_memben_rate_vid != 2334
                                 AND cerm.escalation_type_vid = 3961
                            OR (cerm.escalation_type_vid IS NULL)
                     AND ccbi.record_status = 'A'
                     AND cpd.record_status = 'A'
                     AND ccsd.record_status = 'A'
                     AND cede.record_status(+) = 'A'
                     AND cerm.record_status = 'A'
                     AND NOT EXISTS (
                              SELECT 'X'
                                 FROM clm_escalation_dtl ced1
                                WHERE escal_dt IS NOT NULL
                                  AND ccbi.claims_basic_info_id =
                                                        ced1.claim_basic_info_id
                                  AND ced1.record_status = 'A')) mem_escal,
                (SELECT cerma.escalation_type_vid
                                              additional_escalation_type_vid,
                          cerma.max_escal_rate
                                                     additional_max_escal_rate,
                          cerma.min_escal_rate
                                                     additional_min_escal_rate,
                          cerma.escalation_rate additional_escal_rate,
                          ccbi.claims_basic_info_id claim_basic_info_id,
                          cerma.escalation_basis_vid
                                              additional_esclation_basis_vid,
                          mi_claims_pkg.clm_get_escalation_date_fnc
                              (ccbi.claims_basic_info_id,
                                cpd.escal_applies_to_vid,
                                1,
                                cpd.escal_applies_to_day,
                                cpd.escal_applies_to_month_vid,
                                ccbi.event_dt,
                                ccbi.clm_acceptance_dt
                              ) first_escal_dt,
                          NULL escal_dt
                    FROM clm_claims_basic_info ccbi,
                          clm_claim_scheme_dtl ccsd,
                          clm_plan_dtl cpd,
                          clm_escalation_dtl cede,
                          com_escalation_rate_mst cerma
                  WHERE ccbi.claims_basic_info_id =
                                                        ccsd.claim_basic_info_id
                     AND ccsd.plan_id = cpd.plan_id
                     AND cede.claim_basic_info_id(+) =
                                                      ccbi.claims_basic_info_id
                     AND cede.escal_dt IS NULL
                     AND cpd.is_escal_apply_id = 'Y'
                     AND ccbi.product_id = 4
                     AND cerma.product_id = ccbi.product_id
                     AND cerma.escalation_basis_vid =
                                                      cpd.escal_addben_rate_vid
                     AND (   (    ccbi.claim_status_vid = 2880
                                 AND ccbi.event_dt
                                          BETWEEN cerma.effective_from
                                                AND NVL (cerma.effective_to,
                                                            TO_DATE ('31122999',
                                                                        'DDMMYYYY'
                            OR (    ccbi.claim_status_vid != 2880
                                 AND cede.first_escal_dt
                                          BETWEEN cerma.effective_from
                                                AND NVL (cerma.effective_to,
                                                            TO_DATE ('31122999',
                                                                        'DDMMYYYY'
                     AND (   (    cpd.escal_addben_rate_vid = 2334
                                 AND cpd.escal_addben_perc =
                                                            cerma.escalation_rate
                            OR (    cerma.escalation_type_vid IN
                                                              (3962, 3963, 4442)
                                 AND cerma.escalation_value_by_vid = 4299
                            OR (    cpd.escal_addben_rate_vid != 2334
                                 AND cerma.escalation_type_vid = 3961
                            OR (cerma.escalation_type_vid IS NULL)
                     AND ccbi.record_status = 'A'
                     AND cpd.record_status = 'A'
                     AND ccsd.record_status = 'A'
                     AND cede.record_status(+) = 'A'
                     AND cerma.record_status = 'A'
                     AND NOT EXISTS (
                              SELECT 'X'
                                 FROM clm_escalation_dtl ced1
                                WHERE escal_dt IS NOT NULL
                                  AND ccbi.claims_basic_info_id =
                                                        ced1.claim_basic_info_id
                                  AND ced1.record_status = 'A')) add_escal
        WHERE mem_escal.claim_basic_info_id = add_escal.claim_basic_info_id(+)
      UNION ALL
      SELECT cedo.member_escalation_type_vid
                                                    member_escalation_type_vid,
                cedo.member_max_escal_rate member_max_escal_rate,
                cedo.member_min_escal_rate member_min_escal_rate,
                cedo.member_escal_rate member_escal_rate,
                cedo.claim_basic_info_id claim_basic_info_id,
                cedo.member_esclation_basis_vid
                                                    member_esclation_basis_vid,
                cedo.additional_escalation_type_vid
                                              additional_escalation_type_vid,
                cedo.additional_max_escal_rate
                                                     additional_max_escal_rate,
                cedo.additional_min_escal_rate
                                                     additional_min_escal_rate,
                cedo.additional_escal_rate additional_escal_rate,
                cedo.additional_esclation_basis_vid
                                              additional_esclation_basis_vid,
                cedo.first_escal_dt first_escal_dt,
                cedo.escal_dt escal_dt
         FROM clm_escalation_dtl cedo
        WHERE (cedo.escal_dt, cedo.claim_basic_info_id) =
                    (SELECT   MAX (cedi.escal_dt),
                                 cedi.claim_basic_info_id
                          FROM clm_escalation_dtl cedi
                         WHERE cedi.escal_dt IS NOT NULL
                            AND cedi.escal_dt <= '24-OCT-2013'
                            AND cedi.claim_basic_info_id =
                                                        cedo.claim_basic_info_id
                            AND cedi.record_status =
                                                          'A'
                     GROUP BY cedi.claim_basic_info_id)
          AND cedo.record_status = 'A') ced
WHERE ccbi.policy_id = npm.policy_id
AND ccbi.GROUP_ID = cgm.GROUP_ID
AND ccbi.product_id = cpm.product_id
AND ccbi.claims_basic_info_id = cmd.claims_basic_info_id(+)
AND ccbi.claims_basic_info_id = ca.claim_basic_info_id(+)
AND ccbi.claims_basic_info_id = ccsd.claim_basic_info_id(+)
AND ccsd.plan_id = cpd.plan_id(+)
AND ccbi.claims_basic_info_id = ced.claim_basic_info_id(+)
AND ccbi.record_status = 'A'
AND npm.record_status = 'A'
AND cgm.record_status = 'A'
AND cpm.record_status = 'A'
AND cmd.record_status(+) = 'A'
AND ca.record_status(+) = 'A'
AND cpd.record_status(+) = 'A'
And Ccsd.record_status(+) = 'A'
AND ccbi.claim_number  = 'DAX001';

Answer 1

I would assume this means that it can't find that column in that table.
Usually this is because the column isn't there, the table/view isn't there, or there's no select permissions to the table/view.
To try to narrow this down try:
SELECT CERMA.EFFECTIVE_TO FROM com_escalation_rate_mst cerma
SELECT CERMA.EFFECTIVE_TO FROM com_escalation_rate_mst@db2 cerma
If the synonym and view names are the same, try the first query in both databases or adjust as necessary.
It could also be a permissions issue, like maybe the schema the link uses to DB2 doesn't have select permissions to that view?
As far as to why it stopped working, I have no idea.
You can approach this from bottom up (start with the tables on DB2 and move up)
or top down (start with the synonyms on DB1 and move down)
That will give you an idea of where the issue lies.