Over a year ago I wrote about how to permanently store some of the log information from APEX: http://www.talkapex.com/2009/05/apex-logs-storing-log-data.html APEX 4.0 has some additional columns in APEX_WORKSPACE_ACTIVITY_LOG which you may want to store as well. The following query identifies the new columns:

Note: This query assumes you still have an old instance of APEX 3.2 and a new instance of APEX 4.0 on your database

SELECT column_name
  FROM all_tab_columns
 WHERE owner = 'APEX_040000'
   AND table_name = 'APEX_WORKSPACE_ACTIVITY_LOG'
MINUS
SELECT column_name
  FROM all_tab_columns
 WHERE owner = 'APEX_030200'
   AND table_name = 'APEX_WORKSPACE_ACTIVITY_LOG'
ORDER BY column_name

In case you don't have an old 3.2 instance on your database the new columns are:

CONTENT_LENGTH INTERACTIVE_REPORT_ID IR_SAVED_REPORT_ID IR_SEARCH WS_APPLICATION_ID WS_DATAGRID_ID WS_PAGE_ID

If you permanently store the log information you may want to update your tables and scripts to store the new information.