# XPT V8/V9 Specification
The XPT V8/V9 format extends the original V5 format with support for longer variable names and labels.
> [!WARNING]
> XPT V8/V9 format is **not accepted** for FDA regulatory submissions. For regulatory submissions, use [XPT V5 format](xpt-v5-spec.md) only.
## Key Differences from V5
| Variable name length | 8 bytes | 32 bytes |
| Label length | 40 bytes | 256 bytes |
| Number encoding | IBM float | IEEE 754 |
| Max observations | ~2 billion | Unlimited |
| Regulatory support | FDA/PMDA/NMPA | **Not accepted** |
## Format Overview
XPT V8/V9 maintains the same basic structure as V5:
- **80-byte records** for headers
- **Big-endian** byte order
- **Fixed-width** text fields (space-padded)
However, it differs in:
- **Variable names**: Extended from 8 to 32 characters
- **Labels**: Extended from 40 to 256 characters
- **Numeric encoding**: Uses IEEE 754 instead of IBM floating-point
## Use Cases
V8/V9 format may be appropriate for:
- Internal data storage where longer names improve readability
- Non-regulatory data exchange between systems
- Archival purposes where V5 limitations are problematic
- Academic or research datasets not intended for regulatory submission
## Regulatory Considerations
### FDA Submissions
The FDA Data Standards Catalog explicitly requires XPT V5 format. Files in V8/V9 format will be rejected during technical validation.
### CDISC Standards
CDISC standards (SDTM, ADaM) are designed around V5 limitations:
- Variable names: 8 characters maximum
- Labels: 40 characters maximum
Using V8/V9 format with CDISC data defeats the purpose of standardization.
### Best Practice
If your data requires longer names or labels:
1. Use V5-compliant short names in the XPT file
2. Document full names in define.xml metadata
3. Use controlled terminology for consistency
## Official Specification
**SAS Technical Note: Record Layout of a SAS Version 8 or 9 Data Set in SAS Transport Format**
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src="../assets/pdfs/ts-140-xpt-v8-v9-spec.pdf"
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<p style="text-align: center; margin-top: 10px;">
<a href="../assets/pdfs/ts-140-xpt-v8-v9-spec.pdf" download>Download PDF</a> |
<a href="https://support.sas.com/content/dam/SAS/support/en/technical-papers/record-layout-of-a-sas-version-8-or-9-data-set-in-sas-transport-format.pdf" target="_blank">View on SAS Support</a>
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## xportrs Support
xportrs currently focuses on V5 format for regulatory compliance. V8/V9 support is not a priority as it cannot be used for regulatory submissions.
If you need V8/V9 support for non-regulatory purposes, please [open an issue](https://github.com/rubentalstra/xportrs/issues) to discuss your use case.