The accesslog table definition for Oracle is not consistent with the format of the date values inserted in lib/Request.php. This results in PhpWiki failing.
The attached patch at least allows PhpWiki to run, although the date value is stored as the number of seconds since the epoch. An alternative to the patch is to set ACCESS_LOG_SQL = 0.
A more complete fix requires changing the INSERT statement in Request.php. See the notes in bug http://sourceforge.net/tracker/index.php?func=detail&aid=1569424&group_id=6121&atid=106121