Problem

maxSize parameter cannot be set to -1 in internet/server/classes/RAPServer.properties

Resolution

A permanent solution is applicable only for NEW installations, this will be provided in 3.10

A workaround for existing installations is to manually run the following update statement on the AMG DB:
update P_MT_PAR_DESC set P_MIN_VAL = '-1' where parname='maxSize' and LANGTEXTKEY='internet_server_classes_RAPServer_properties_MAXSIZE'