A mainframe formatted sequential file is a binary image of a mainframe file with variable length records. The COBOL Input tool supports two types:
-
Mainframe V: the data set contains variable-length records. The four bytes preceding the logical record is the Record Descriptor Word. The content is as follows.
|
Bytes |
Description |
|
1-2 |
Length of the logical record plus the length of the four-byte Descriptor Word. |
|
3-4 |
Usually low values. |
-
Mainframe VB: the data set contains variable-length blocked records. The four bytes preceding the logical record (Descriptor Word) are as follows.
|
Bytes |
Description |
|
1-2 |
Length of the logical record plus the length of the four-byte Descriptor Word. |
|
3-4 |
The length of the block including four-byte Descriptor Word. |
The COBOL Input tool doesn’t support Mainframe VBS (variable-length spanned) records (logical records that extend across more than one block).