Control Record Formats
A 32-byte prefix precedes each control record. The format of this prefix is defined in Table 1.
| Field | Field Name | Position | Size | Type |
|---|---|---|---|---|
| 0 | Record Length | 01 - 04 | 4 | Binary |
| 1 | Document Type | 05 - 12 | 8 | A |
| 2 | Item Sequence Number- 12 | 13 - 24 | 12 | N |
| 3 | Reserved | 25 - 32 | 8 | B |
The record length is a 4-byte integer indicating the size of this record, including these 4 bytes, in big endian format. The document type is an 8-character identifier for this type of record. Tracers have a document type of IBMTRACR. Dividers have a document type of IBMDIVDR. User documents are either USRITEM or USRRECRD, depending on whether or not they have a unique ISN, respectively.