Built on Azure Data Lake Storage Gen2, it is the one logical data lake for an entire Microsoft Fabric tenant, provisioned automatically, and the place where every Fabric workload keeps its data.
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Terms in this definition
- ADLS Gen2
Short for Azure Data Lake Storage Gen2: a standard GPv2 account with hierarchical namespace turned on, so analytics workloads get true directories and POSIX-style ACLs.
- Logical
Independent of any implementation. Each logical design is made real through a physical counterpart.
- Data lake
Holds files of every kind, structured, semi-structured or unstructured, usually spread over a distributed file system, and lets engines like Spark apply a schema when reading. In Azure this is Data Lake Storage: Blob Storage with a hierarchical namespace enabled.
- Microsoft Fabric
Analytics platform from Microsoft delivered as SaaS on top of OneLake, offering capabilities including Direct Lake and shortcuts.
- Tenant
A trusted, dedicated Microsoft Entra ID instance that stores the users, groups and app registrations of one organisation. A subscription trusts only a single tenant, although a tenant can be trusted by several subscriptions.
- WHERE
Limits a SELECT, UPDATE or DELETE to just the rows meeting a condition. Omit it, and the statement hits every row.
- Fabric workload
Microsoft Fabric groups its features into workloads, each serving a role or job, for instance Power BI, Real-Time Intelligence, Data Warehouse, Data Factory or Data Engineering; they all read and write the same OneLake data.
Related terms
- AWS IAM
Amazon's service for controlling who can sign in and what they may do across AWS. OneLake's Amazon S3 shortcuts depend on it: the cloud connection behind such a shortcut stores an IAM user's secret access key and its key ID.
- Cold start
The extra time a Fabric warehouse query can take on its first run, because data has to be pulled from OneLake into the cache, statistics built or nodes woken up. In query insights, a
data_scanned_remote_storage_mbvalue above zero is the tell-tale sign. - Cosmos DB in Fabric
A document-style NoSQL database living inside Fabric, optimised for AI workloads and running on Azure Cosmos DB technology. Fabric copies its contents into OneLake as Delta tables without any setup, so they can be queried through a SQL analytics endpoint.
- Data retention policy
Automatically deletes KQL database or table data once it's older than a configured age (by default 3,650 days). You set it in Manage > Data policies, next to the caching policy, and it applies to the OneLake copy of the data too.
- DFS endpoint
Data Lake Storage Gen2 address in the form https://<account>.dfs.core.windows.net. Use this one, not the blob address, when creating OneLake shortcuts or setting up trusted workspace access to an ADLS Gen2 account.
- Direct Lake
Mode for Fabric semantic models that loads Delta or Parquet files from OneLake straight into VertiPaq, giving almost import-level performance without duplicating data.
- Direct Lake on OneLake
Recommended choice for new Direct Lake models: it pulls Delta tables from one or several Fabric items via OneLake APIs, with OneLake security applied, allows composite models and never switches to DirectQuery.
- Fabric events
Events raised by Fabric itself and listed in Real-Time hub, for example about workspace items, OneLake, jobs or capacity overview. An eventstream can carry them onward, or Activator can raise alerts from them.