declaring a text field in ztable

dear all,

iam trying to declare a text field for inserting comments in a ztable. first iam declaring it in a code and updating it in to a ztable through program. this text field is given in alv as edit mode than tere some text is maintained in output(i.e in editable alv) than user when clicks save than total records r updated to ztable.

my problem is that this text field is taking only 5 to 6 letters as input.

With regards,

Prasadbabu.