6 Troubleshooting XStream

Is an OCI Client Application Unable to Attach to the Outbound Server?

If a client application cannot attach to an outbound server using the Oracle Call Interface (OCI) OCIXStreamOutAttach() function, then the following conditions might be causing the problem:

• The client application is not connected to the outbound server's database as the outbound server's connect user. The client application must connect to the database as the connect user before attaching to the outbound server.

• The client application is not passing a service handle to the outbound server. Ensure that the client application is passing a service handle using the OCISvcCtx and not OCIServer.

Are Changes Failing to Reach the Client Application in XStream Out?

In an XStream Out configuration, if database changes that should be captured and streamed to the client application are not reaching the client application, then the capture process might have fallen behind, or there might be problems with rules or rule-based transformations.

COLUMN CAPTURE_NAME HEADING 'Capture|Name' FORMAT A15
COLUMN CREATE_MESSAGE HEADING 'Last LCR|Create Time'
COLUMN ENQUEUE_MESSAGE HEADING 'Last|Enqueue Time'

SELECT CAPTURE_NAME,
       TO_CHAR(CAPTURE_MESSAGE_CREATE_TIME, 'HH24:MI:SS MM/DD/YY') CREATE_MESSAGE,
       TO_CHAR(ENQUEUE_MESSAGE_CREATE_TIME, 'HH24:MI:SS MM/DD/YY') ENQUEUE_MESSAGE
  FROM V$STREAMS_CAPTURE;

Are LCRs Streaming from an Outbound Server Missing Extra Attributes?

Logical change records (LCRs) can contain the following extra attributes related to database changes:

• row_id

• serial#

• session#

• thread#

• tx_name

• username

By default, a capture process does not capture these extra attributes. If you want extra attributes to be included in LCRs streamed from an outbound server to a client application, but the LCRs do not contain values for extra attributes, then make sure the capture process that captures changes for the outbound server is configured to capture values for the extra attributes.

To configure a capture process to capture one or more of these extra attributes, use the INCLUDE_EXTRA_ATTRIBUTE procedure in the DBMS_CAPTURE_ADM package.

Is the Client Application Unresponsive?

If the client application is unresponsive, then the Streams pool size might be too small. Run the following query at the database that contains the outbound server or inbound server:

SELECT STATE FROM V$PROPAGATION_RECEIVER;

If the state is WAITING FOR MEMORY, then consider increasing the Streams pool size.

You can also run the following query:

SELECT TOTAL_MEMORY_ALLOCATED/CURRENT_SIZE FROM V$STREAMS_POOL_STATISTICS;

If the value returned is 0.90 or greater, then consider increasing the Streams pool size.

For an outbound server that receives changes from a capture process that is running on the same database, you can also run the following query:

SELECT STATE FROM V$STREAMS_CAPTURE;

If the state is WAITING FOR BUFFER QUEUE TO SHRINK, then increase the Streams pool size.

You can increase the Streams pool size by modifying the STREAMS_POOL_SIZE initialization parameter, or by modifying other initialization parameters related to memory.

Otherwise, if there is enough memory in the Streams pool, then check your client application for programming errors.

Is XStream In Unable to Identify an Inbound Server?

If an XStream In configuration cannot identify an inbound server, then the following error is returned:

ORA-26840: STREAMS unable to identify an apply for the source database "%s"

This error indicates that there are multiple subscribers to the queue used by the inbound server. Subscribers can include inbound servers, outbound servers, apply processes, and propagations.

To determine whether there are multiple subscribers to the inbound server's queue, run the following query on the inbound server's database:

SELECT APPLY_NAME SUBSCRIBER, QUEUE_NAME FROM DBA_APPLY UNION
  SELECT PROPAGATION_NAME, SOURCE_QUEUE_NAME
  FROM DBA_PROPAGATION
  ORDER BY QUEUE_NAME;

You can add a WHERE clause to the query to limit the output to the inbound server's queue.

If the query returns more than one subscriber to the inbound server's queue, then reconfigure the subscribers so that the inbound server is the only subscriber.