Debunking Myths related to Table Structure in Dynamics 365 Business Central 2026 Wave 2
This post debunks common myths about table structure limits in Dynamics 365 Business Central 2026 Wave 2 (version 29), which now merges table extension fields into base tables. It clarifies field count limits (1018 fields), SQL Server 8KB record size constraints based on data types, key/index limits (no 40-key cap), and the possibility of mixing base and extension fields in indexes.
post Dynamics 365 Business Central tales, myths, legends. And something serious.
"All 3rd party app fields are now part of the base table."
Key points
- In version 29, all third-party app fields are now part of the base table with no separate table extension joins
- Maximum of 1018 regular fields can be defined in a table (1024 SQL columns minus 6 system fields)
- The 8KB SQL Server limit applies only to primitive data types; text and code fields use pointers and can exceed this
- The 40-key limit from CSIDE no longer applies; SQL Server allows up to 999 indexes
- Base table fields and extension fields can be mixed in the same index, with some constraints across different apps
Quotes
- “All 3rd party app fields are now part of the base table.” (This is a fundamental architectural change in version 29 that affects how developers design and extend tables)
- “1024 is the maximum column definition allowed by SQL Server.” (Understanding the SQL Server hard limit helps developers plan field counts without hitting deployment errors)
- “Text and Code they don’t. They are SQL NVARCHAR, hence their data can be of super large dimension.” (Clarifies that the 8KB record limit is conditional on data type, not an absolute constraint for all fields)
Context
- Features: table extensions, field definitions, index creation, table record sizing, field type storage
- Versions: 29, 2026 Wave 2
Source: Duilio Tacconi, community blog. Summary, key points and quotes are derived (CONTENT-NOTICE.md); read the original for the full text.