Format: ansLength: ..17Variable (LLVAR — 2-digit length prefix)
DE 101
File Name
What it is
Name of the file targeted by a file-update (0300) message — e.g. a negative/hot-card file.
Specification reference
Defined in ISO 8583:1987 (base). Card networks publish their own dialect tables (Visa BASE I / V.I.P., Mastercard CIS) that refine formats, lengths, and — for private-use elements — the entire layout. Always confirm against the interface specification you implement.