Options for including before values in messages for publications

When an update occurs in columns that are not part of the target key, the Q Capture program either sends the value in the column after the change occurred, or it sends both the value in the column before the change occurred and the value in the column after the change occurred. When an update occurs in a key column, the before value and after value are always sent.

Because a delete operation always applies to a row and not to a specific column value, deletes are handled differently. For deletes, only before values are ever sent. Before values of key columns are always sent. If you specify for the message to include column values from before and after the change, then, if values in non-key columns are deleted, the before values of the non-key columns are sent.

The sections below describe your two options for before values and after values:

Send new data values only

By default when an update occurs at the source table, the Q Capture program publishes the values that are in the non-key columns after the change occurs. If you specify for the message to include only new data values (values from after the change), then the message does not include the values that were in the non-key columns before the change occurred.

Recommendation: If the application that receives the messages for the publications never uses the value that was in each non-key column before the change, then specify that the Q Capture program send only column values from after the change.

Send both old and new data values

If you specify that the message is to include both old and new data values (values from both before and after the change), then when a non-key column is updated, the Q Capture program publishes the value that is in the column before the change occurs and the value that is in the column after the change occurs.

Recommendation: If the application that receives the messages for the publications uses the value that was in each column before the change, then specify for the Q Capture program to send column values from before and after the change.
Restrictions for LOB data types: Before values for columns with LOB data types are not sent in the messages. If you specify for the message to include both before and after values, then this option does not apply for columns with LOB data types, and their before values are not sent.