TOM Compatibility Levels

The missing documentation.

Ever since the convergence of Analysis Services (Tabular) and Power BI (Premium) has started, the Analysis Services API surface has evolved rapidly. New versions of the TOM client libraries are being released frequently, and new Power BI (Premium) features introduce new TOM Compatibility Levels which must be configured at the database in order to enable certain features in the underlying engine.

However, official documentation of those feature sets and the corresponding compatibility levels and NuGet versions is very sparse.

Using the reflection approach described in this article, this page provides "The Missing Documentation" - a chronological listing of TOM features by compatibility level. Major features are annotated with related articles and blog posts.

API Changes in 19.65.7 - 6-Jul-2023

No changes in public API

API Changes in 19.65.4 - 8-Jun-2023

No changes in public API

API Changes in 19.64 - 4-May-2023

  • Release of TMDL Preview-2 [NetCore]

  • REMOVED: CalculationGroup.DefaultExpression property (Preview)

  • REMOVED: CalculationExpression class (Preview)

  • ADDED: CalculationGroupSelectionMode enum (Preview)

  • ADDED: CalculationGroupExpression class (Preview)

  • ADDED: CalculationGroup.MultiSelectionExpression property (Preview)

  • ADDED: CalculationGroup.NoSelectionExpression property (Preview)

API Changes in 19.61 - 6-Apr-2023

  • Release of TMDL Preview-1 [NetCore]

  • NEW MetadataObject types:

    • Calendar (Preview)

    • TimeUnitColumnAssociation (Preview)

    • CalendarColumnReference (Preview)

  • ADDED: TimeUnit enum (Preview)

1604 (new in 19.60 - 16-Mar-2023)

API Changes in 19.60

1603 (new in 19.57 - 9-Feb-2023)

  • DataCoverageDefinition MetadataObject type: A tabular DataCoverageDefinition object. The expression defined on this object gives hint about the data in a partition.

  • Partition.DataCoverageDefinition: A reference to an optional DataCoverageDefinition that provides the hint regarding the data that is covered by the partition.

API Changes in 19.55 - 11-Jan-2022

No changes in public API

API Changes in 19.54 - 8-Dec-2022

No changes in public API

API Changes in 19.52 - 10-Nov-2022

  • The execution flow of ApplyRefreshPolicy is the same as the flow that is triggered by a call to RequestRefresh, followed by a call to Model.SaveChanges.

  • The execution flow includes:

    • Calculating the expected partitioning scheme based on the effective date.

    • Comparing the expected partitioning scheme to the existing set of partitions and issue the needed changes to move to the expected scheme [dropping, creating, and merging partitions as needed].

    • Refresh the newly created partitions as well as the existing partitions in the incremental window.

  • The only difference between the ApplyRefreshPolicy and the combination of RequestRefresh+SaveChanges is ApplyRefreshPolicy enables advanced options that are not available otherwise.

  • It is recommended to use ApplyRefreshPolicy when you want to use a single API call, especially with advanced options.

  • It is recommended to use the combination of RequestRefresh + SaveChanges when you want to combine the operation with additional authoring calls in the model before the call to SaveChanges.

API Changes in 19.51 - 6-Oct-2022

No changes in public API

1601 (new in 19.49 - 19-Sep-2022)

Introduces FormatStringDefinition to measures. Previously, those only existed on Calculation Items.

API Changes in 19.48 - 15-Aug-2022

1572 (new in 19.46 - 11-Jul-2022)

1571 (new in 19.42 - 20-Jun-2022)

1570 (new in 19.42 - 20-Jun-2022)

API Changes in 19.39 - 13-Apr-2022

1569 (new in 19.36 - 01-Mar-2022)

1568 (new in 19.36 - 01-Mar-2022)

  • Model.MaxParallelismPerRefresh: Determines the max possible number of parallel tasks in data refresh, within the resource constraints of the hosting service.

1567 (new in 19.34 - 10-Feb-2022)

1566 (new in 19.27 - 10-Nov-2021)

1565 (new in 19.26 - 08-Sep-2021)

Hybrid Tables in PBI Premium

API Changes

  • RefreshPolicyMode (Enum)

    • RefreshPolicyMode.Import: Creates import partitions during incremental refresh.

    • RefreshPolicyMode.Hybrid: Creates import and DirectQuery partitions during incremental refresh.

1564 (new in 19.22 - 02-Jun-2021)

1563 (new in 19.20 - 07-Apr-2021)

1562 (new in 19.16 - 15-Jan-2021)

Auto Aggregations

API Changes

  • Table.SystemManaged: A boolean value that indicates whether the table is managed by the system. The system takes ownership of creation and deletion of such tables.

1561 (new in 19.14 - 08-Dec-202)

1560 (new in 19.12 - 12-Oct-2020)

1550 (new in 19.9 - 10-Aug-2020)

  • SourceLineageTag (Column, Hierarchy, Level, Measure, NamedExpression, Table): A tag that represents the lineage of the source for the object.

1545 (new 19.6 - 14-Jul-2020)

  • NamedExpression.ParameterValuesColumn: Client tools apply filters to this column using M parameter. The presence of this property indicates model owner allows Dax queries to override this parameter, and columns data type must match the type specified in the meta tag of the parameter.

1540 (new 19.4 - 16-Jun-2020)

  • LineageTag (Column, Hierarchy, Level, Measure, NamedExpression, Table): A tag that represents the lineage of the object.

1535 (new in 19.2 - 01-Jun-2020)

1520 (max level in 18.4)


  • Model.DataSourceDefaultMaxConnections: DataSourceDefaultMaxConnections will be used for connections to a data source if MaxConnections is set to -1 on the data source object or if there is no corresponding data source object for the data source.




  • Model.QueryGroups: Gets the collection object of all querygroups in the current Model.

  • NamedExpression.QueryGroup: QueryGroup associated with the expression.

  • Partition.QueryGroup: QueryGroup associated with the partition.

  • Table.ExcludeFromModelRefresh: A boolean value that indicates whether the table is excluded from model refresh. When this is true, a refresh operation on the model would not trigger a refresh on the partitions of the table if they were already processed.



Calculation Groups

API Changes


"Enhanced Metadata Format"

API Changes



Dual Storage Mode

API Changes

  • ModeType.Dual: Allows support for dual mode of Import as well as DirectQuery.

  • Measure.DataCategory: Specifies the type of data contained in the measure so that you can add custom behaviors based on measure type.


Incremental Refresh Policy (Import)

API Changes

Earlier Versions

  • 1100, 1103, 1200, 1400

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