XPT V5 Specification

The XPT V5 format is defined by the SAS Technical Note TS-140. This page provides a comprehensive overview of the format.

Format Overview

XPT V5 (also known as SAS Transport Version 5) is a binary file format with:

• 80-byte records for headers
• Big-endian byte order
• IBM floating-point number encoding
• Fixed-width text fields (space-padded)

graph TB
    subgraph "XPT V5 File Structure"
        LH[Library Header<br/>80 bytes] --> FD[First Dataset]
        FD -->|" More datasets "| ND[Next Dataset...]
    end

subgraph "Dataset Structure"
MH[Member Header<br/>80 bytes] --> DH[DSCRPTR Header<br/>80 bytes]
DH --> DD[Dataset Descriptor<br/>160 bytes]
DD --> NH[NAMESTR Header<br/>80 bytes]
NH --> NR[NAMESTR Records<br/>140 bytes × n]
NR --> OH[OBS Header<br/>80 bytes]
OH --> OD[Observation Data]
end

Library Header

The file begins with a library header identifying the format:

#![allow(unused)]
fn main() {
const LIBRARY_HEADER: &[u8; 80] =
    b"HEADER RECORD*******LIBRARY HEADER RECORD!!!!!!!000000000000000000000000000000  ";
}

Member Header

Each dataset (member) begins with a member header:

The numbers at the end indicate:

• 00000016 = 16 bytes for dataset descriptor (hex)
• 0000014 = 140 bytes per NAMESTR record (decimal)

Dataset Descriptor

The dataset descriptor contains:

Second Descriptor Record

NAMESTR Records

The NAMESTR header introduces the variable metadata:

Each variable is described by a 140-byte NAMESTR record. See NAMESTR Records for detailed byte layout.

Observation Data

The observation header introduces the data:

After this, raw observation data follows in row-major order:

[Row 1: Var1][Row 1: Var2]...[Row 1: VarN]
[Row 2: Var1][Row 2: Var2]...[Row 2: VarN]
...

Numeric Variables

All numeric variables are stored as 8-byte IBM floating-point:

• 8 bytes per value
• Big-endian byte order
• IBM base-16 exponent (not IEEE 754)

Character Variables

Character variables are stored as fixed-width text:

• 1-200 bytes per value (as defined in NAMESTR)
• Space-padded on the right
• No null terminators

Missing Values

Record Padding

XPT uses 80-byte record alignment:

• NAMESTR records: 140 bytes (not aligned)
• Multiple NAMESTRs fill to 80-byte boundary
• Observation rows: variable length (row_length × n)
• File ends with space padding to 80 bytes

Version Differences

[!IMPORTANT] For regulatory submissions, only V5 format is accepted. xportrs focuses on V5 compliance.

Official Specification

The authoritative source for XPT V5 format is:

SAS Technical Note TS-140: Record Layout of a SAS Version 5 or 6 Data Set in SAS Transport (XPORT) Format

Download PDF | View on SAS Support

Format Family

The Library of Congress maintains format documentation:

• XPT Format Family
• XPT V5 Specific