Hello lokeshheda and welcome to the forums,
Because occure clause is relted to occuranc of file(data) and not of records,as 01 level is use to define record so...
There is more to an 01 than this.
The 01(s) of an FD are
the record definitions.
An 01 may be used in Working Storage as well as the Linkage Section.
In all cases, an 01 may not have an occurs.