Tape Format

Tapes made by IRIS hold exact images of corresponding disk-based product files. The tapes are always written using fixed-length 6144-byte records, where the last tape record is padded with zeros, if necessary, to the full 6144-byte length.

Products are separated on tape by end-of-file (EOF) marks.

Because disk product files begin with a product_hdr structure, this is also the structure initially encountered in the first record of each product on tape. By examining the headers, you can determine what kinds of product files have been stored on the tape.

There is a special short record at the beginning of the tape that serves to identify how and when the tape was initially created by the init_iris_tape utility. This record contains the tape_header_record structure, and is followed by an EOF and the product files, if any. There are no special directory or inventory records on the tape.

After a tape has been started, the only additional writing that can be done is to append more product file images to the end.