Caused by: intradoc.data.DataException: !csJdbcGenericError | Oracle webcenter webservice

I'm getting this error !csServiceDataException,GET_WORKFLOW_HISTORY_EMAIL_DETAILS,QWorkflowHistoryEmailDetails!$ exception backtrace:intradoc.common.ServiceException: !csServiceDataException,GET_WORKFLOW_HISTORY_EMAIL_DETAILS,QWorkflowHistoryEmailDetails!$ services/3 *ScriptStack GET_WORKFLOW_HISTORY_EMAIL_DETAILS."Caused by: intradoc.data.DataException: !csJdbcGenericError" while executing a custom service in oracle webcenter. let me know what i 'm missing. if query & service i'm using is correct(given below). or if there is something else i'm missing

**Service**

<tr>
    <td>GET_WORKFLOW_HISTORY_EMAIL_DETAILS</td>
    <td>Service
        33
        null
        null
        null<br>
        !csUnableToGetRevInfo</td>
    <td>5:QWorkflowHistoryEmailDetails:WorkflowActionHistory::Unable to get workflow history</td>
</tr>

**Query**

    <tr> <td>QWorkflowHistoryEmailDetails</td> 
<td>SELECT WorkflowHistory.*,
      Reason.Reason,
      ApprovalType.ApprovalType
      CASE
        WHEN APPROVALTYPE IS NULL
        THEN XPURPOSEFORREJECTION
      END AS APPROVALTYPE,
      CASE
        WHEN NVL(daction,'')='sendTo'
        THEN 'Approve'
      END AS daction
    FROM WorkflowHistory WorkflowHistory,
      Reason Reason,
      ApprovalType ApprovalType
    WHERE UPPER(dDocName)     = UPPER(?)
    AND xPurposeForSubmission = Reason.ReasonID(+)
    </td>
    </td> 
        <td>dDocName varchar</td>
    </tr>

I believe this error is because i have copy/pasted a new query in my query template, i will have to make few more changes either in configuration or any other file, which i'm not sure of. i'm using a simple query, as below, now but getting the same error.Any help on how to add a new query and proceed

<td>
SELECT 
 DACTIONDATE
FROM WorkflowHistory
WHERE UPPER(dDocName)     = UPPER(?)
AND daction             IN('SendTo','Approve')
ORDER BY dActionDate DESC,dActionMillis;
</td> 
    <td>dDocName varchar</td>