File transfer
Moving data between the mainframe and other systems, where character encoding and record structure both need attention.
Also written FTP, data transfer
Getting data on and off the mainframe is routine work, and it has two wrinkles that catch people out.
The first is encoding. The mainframe stores text in EBCDIC while almost everything else uses ASCII or UTF-8. A transfer done in text mode translates between them; one done in binary mode does not. Choosing wrongly gives you either unreadable characters or corrupted binary data, and the symptom looks the same from a distance.
The second is structure. A dataset is made of records with a defined length, while a file on another system is a stream of bytes with line endings. Something has to reconcile the two, either the transfer tool or a conversion step at one end.
The mechanisms themselves are ordinary: FTP and SFTP, managed file transfer products at larger sites, and increasingly Unix System Services, where standard Unix tooling can be used directly.
When a transferred file looks wrong, check the mode and the record format before anything else. It is almost always one of those two.
Related terms
- EBCDICThe character encoding mainframes use, where letters and numbers are stored as different byte values than on a laptop.
- DatasetWhat a mainframe calls a file: a named collection of records with a defined structure, rather than a loose stream of bytes.
- Unix System ServicesA full Unix environment built into z/OS, with a shell, directories and files alongside the traditional mainframe world.
- Record formatWhether the records in a dataset are all the same length or vary, and how they are blocked. Written as RECFM.