REWRITE STATEMENT:
As in the situation of a relative file, the REWRITE statement needs that the file should be opened in the I-O mode, and if the SEQENTIAL access mode is specific, the value of the record key of the record being replaced should be equal to that of the record last from this file.
The INVALID KEY condition occurs in the cases as shown below:
(i) Whenever the record key does not match that of an existing record in the file.
(ii) For the SEQUENTIAL access, whenever the value of the record key is not similar to that of the last record read from the file.