when I draw a schematic,
I use: option->schematic page properties to change the page size,there i receive an automatic small box at the corner of the circuit,mentioning the data about the circuit.(Title,date,number,sheet,size,rev)
hi tamil,
first understand clearly that is title block for schematic and title block will not come in net list file. Net list contain only symbol with net only better study the user guide.
If you want title block in your layout tool than u need draw u own using some 2D tools and import the DXF in to allegro..
or if you are looking for increasing the size of the drawing extents i.e working area then
go to setup --> design Parameters -->Design --> chnage the size in Extents tab..