You need to increase the maximum allowed file size on your server:
For modplsql the default the setting for PlsqlMaxParameters is 2000 which equates to about a 5.75M file. To increase the allowed file size modify your DAD configuration in the $ORALCE_HOME/ohs/modplsql/conf/dads.conf file or $ORALCE_HOME/Apache/modplsql/conf/dads.conf file and set PlsqlMaxParameters to a higher value.
For the APEX listener you need to increase "maxPostSize" on your web server. For Glassfish the default value is 2097152 bytes. To in crease it on glassfish you can find it under "Network Config"->"Network Listeners"->"http-listenerX"