Question & Answer
Question
When C:D z/OS transfers a VB file there are 4 extra bytes at the beginning of the record that are not there when transferring the same VB file with FTP. What are these extra bytes in the C:D z/OS transfer record?
Answer
When transferring a VB file from C:D z/OS to a non-mainframe platform in DATATYPE=BINARY with RECFM=U the BDW (Block Descriptor Word) and RDW (Record Descriptor Word) will be included in the data; the file is no longer treated as a VB file so the BDW/RDW is included as part of the data for the record. Each record will begin with a RDW, along with a BDW in front of it, when the first record is encountered within each block of records. The RDW/BDW are needed if the file is going to be transferred back to the original CDZ or to another CDZ so that the file can be built correctly on the z/OZ system.
However, when transferring a VB file with FTP from z/OS to a non-mainframe platform in BINARY format the BDW/RDW will be stripped out unless you specify RDW. Even then the BDW may or may not be included.
A VB record transferred by CDZ with DATATYPE=BINARY and RECFM=U coded in the process will look similar to the following:
CD: 00000000 7D 22 00 00 04 76 00 00 00 00 00 0C F1 40 40 40 40 40 40 40 40 40 40 40
The x'7D 22 00 00' is the BDW specifying a block size of 32034. The x'04 76 00 00' is the RDW specifying a record size of 1142 for this record. The next record behind this in the block will only have a RDW and it could be the same or it could be larger or smaller. This will continue with each record until the first record of the next block is read.
The same record transferred with FTP will look similar to the following:
FTP: 00000000 04 76 00 00 00 00 00 0C F1 40 40 40 40 40 40 40 40 40 40 40
The x'04 76 00 00' is the RDW of this record specifying that the LRECL is 1142. There is no BDW in this record.
However, when transferring a VB file with FTP from z/OS to a non-mainframe platform in BINARY format the BDW/RDW will be stripped out unless you specify RDW. Even then the BDW may or may not be included.
A VB record transferred by CDZ with DATATYPE=BINARY and RECFM=U coded in the process will look similar to the following:
CD: 00000000 7D 22 00 00 04 76 00 00 00 00 00 0C F1 40 40 40 40 40 40 40 40 40 40 40
The x'7D 22 00 00' is the BDW specifying a block size of 32034. The x'04 76 00 00' is the RDW specifying a record size of 1142 for this record. The next record behind this in the block will only have a RDW and it could be the same or it could be larger or smaller. This will continue with each record until the first record of the next block is read.
The same record transferred with FTP will look similar to the following:
FTP: 00000000 04 76 00 00 00 00 00 0C F1 40 40 40 40 40 40 40 40 40 40 40
The x'04 76 00 00' is the RDW of this record specifying that the LRECL is 1142. There is no BDW in this record.
Related Information
[{"Product":{"code":"SSFGBN","label":"IBM Sterling Connect:Direct for z\/OS"},"Business Unit":{"code":"BU059","label":"IBM Software w\/o TPS"},"Component":"--","Platform":[{"code":"PF035","label":"z\/OS"}],"Version":"5.2","Edition":"","Line of Business":{"code":"LOB59","label":"Sustainability Software"}}]
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Document Information
Modified date:
26 May 2020
UID
swg22011602