What Is OneStream?
OneStream is a Corporate Performance Management (CPM) platform. If you have been dropped into a OneStream project, you may know it as "the system Finance uses for budgets and consolidation." That is accurate — but it only scratches the surface. This guide explains what the platform does, how its major subsystems fit together, and where you, as a developer, spend most of your time.
A Unified CPM Platform
Corporate Performance Management covers the processes a finance organization uses to plan, close, consolidate, and report on financial data. Before platforms like OneStream, a typical enterprise juggled a patchwork of tools:
- A General Ledger / ERP for actuals (SAP, Oracle, NetSuite)
- A consolidation tool for multi-entity roll-ups (Hyperion Financial Management, SAP BPC)
- A planning tool for budgets and forecasts (Hyperion Planning, Anaplan, Adaptive Insights)
- Spreadsheets — often dozens — for driver models, allocations, and ad-hoc analysis
- A reporting layer (Power BI, Tableau, or yet another Hyperion product)
- Custom scripts and ETL jobs gluing everything together
Each tool has its own data model, its own security, and its own integration points. Reconciling data across them is a recurring headache.
OneStream replaces this patchwork with a single platform. Actuals, budgets, forecasts, consolidation, reporting, and data integration all live in one application, operating against one shared data model. The same cube that receives actuals from the GL also accepts journal entries and top-side adjustments during the close cycle, and budget driver input during the planning cycle. Variance reports do not require cross-system reconciliation — all financial data shares the same dimensions, the same hierarchies, and the same security model.
The Seven Engines
Under the hood, OneStream is organized into seven cooperating engines. Each engine owns a distinct part of the platform's functionality. As a developer, you interact with some engines directly (writing Business Rules that call their APIs) and others indirectly (configuring them through the application UI).
| Engine | What It Does | Developer Touchpoint |
|---|---|---|
| Finance Engine | Cube storage, calculation, consolidation, currency translation | Finance Business Rules, Member Formulas, api.Data.Calculate |
| Stage Engine | Staging tables for imported data before it enters the cube | Transformation rules, Connector/Parser Business Rules |
| Workflow Engine | Controls the process lifecycle — who can input data, when it is locked, and approval routing | Workflow profiles, Scenario Types, Workflow Event Handlers |
| Data Quality | Certification, validation checks, and lock/unlock controls | Data Quality Event Handlers, certification rules |
| Data Management | Orchestrates sequences of steps — import, transform, load, calculate, export | Data Management steps, Extender Business Rules |
| BI Blend | Brings operational (non-cube) data into dashboards and reports alongside financial data | BI Blend data sources, Dashboard DataSet rules |
| Presentation / BRApi | Dashboards, Cube Views, reports, and the full Business Rule API surface | Dashboard rules, XFBR string functions, BRApi calls |
Extensibility
OneStream's defining characteristic for developers is its extensibility. The platform ships with powerful built-in engines, but nearly every behavior can be customized or extended through code.
Dimensions — Beyond the fixed dimensions (Entity, Account, Time, Scenario, Flow, Consolidation, Origin, Intercompany), OneStream provides eight User-Defined dimensions (UD1 through UD8). These let you model any analytical axis your business requires — Department, Product Line, Region, Project, Customer Segment — without modifying the core schema.
Business Rules — Custom logic written in VB.NET (or C# for most rule types) that runs server-side inside the OneStream application. Business Rules are the primary mechanism for extending the platform. They cover calculations, data integration, dashboard behavior, event handling, and more.
Cubes — A single application can contain multiple cubes, each with its own dimensional structure. A common pattern is one main cube (the "parent" or corporate cube) with detail cubes underneath that roll up into it — for example, separate cubes for different business units, regions, or planning processes like workforce or capital projects. Data flows from the detail cubes into the parent cube during consolidation, giving leadership a unified view while each area maintains its own dimensional structure.
MarketPlace Solutions — Pre-built solutions (People Planning, Capital Planning, Account Reconciliations, Tax Provisioning, and others) that install into your application and provide ready-made dashboards, rules, and dimension structures. These are extensible themselves — you can modify their Business Rules and add custom logic on top.
Inputs and Outputs: A Developer's Perspective
At the highest level, a OneStream implementation is a pipeline. Data flows in from source systems, gets transformed and loaded, gets calculated and consolidated, and then gets presented to users. As a developer, your job is writing the Business Rules that control each stage of this pipeline.
Walking through this flow for a typical FP&A cycle:
- Import — A Data Management sequence pulls actual financial data from the ERP (and possibly HR data, sales data, etc.) into OneStream's staging tables.
- Transform — Transformation rules map source accounts and entities to the OneStream dimension structure, handle sign conventions, and validate the data.
- Load to Cube — Clean data moves from staging into the multidimensional cube under the Actual scenario. During the close cycle, the cube also receives journal entries and manual adjustments — these are written to the AdjInput Origin member so they remain separate from system-loaded data.
- Seed — Actual data is copied to the Budget or Forecast scenario as a starting point for planning.
- Input — Users enter data directly into the cube through journal entries, Cube Views configured for form entry, and custom dashboard components. For planning, this means driver assumptions (growth rates, headcount changes, pricing). For close and consolidation, this includes top-side adjustments and reclassifications.
- Calculate — Finance Business Rules multiply drivers by rates, apply growth factors, and compute the full P&L.
- Consolidate — The Finance Engine rolls up entity-level data to parent entities, handles currency translation, and processes intercompany eliminations.
- Report — Dashboards and Cube Views present budget-vs-actual variance, forecast trends, and drill-down analysis.
Each numbered step above involves Business Rules, configuration, or both. The guides that follow in this series walk through each step in detail.
Introducing ABC Manufacturing
Throughout this guide series, we use a fictional company — ABC Manufacturing — to ground every concept in a realistic FP&A scenario.
About ABC:
- A mid-size manufacturer with three operating entities: US_Corp (United States), EMEA_Sub (Europe), and APAC_Sub (Asia-Pacific)
- Each entity runs its own ERP: SAP (US), Oracle (EMEA), and NetSuite (APAC)
- The FP&A team is building their annual budget and a rolling 12-month forecast in OneStream, replacing a collection of Excel workbooks and an aging Hyperion Planning instance
What ABC needs to build:
- Data integration — Pull actuals from three different GL systems into one cube, mapping three different charts of accounts to a unified Account dimension
- Annual budget — Department managers input driver assumptions (headcount, salary rates, sales volumes, pricing) and the system calculates a full P&L by entity and department
- Rolling forecast — Each month, the team seeds actuals into Forecast_Working, projects open months, and saves the result to a monthly snapshot (Forecast_M1 through Forecast_M12) for historical comparison
- Variance analysis — Budget vs. Actual and Forecast vs. Actual dashboards that the CFO reviews monthly
- People Planning — An employee-level headcount plan that feeds salary and benefits expense into the main P&L forecast
Each guide in this series builds a piece of this solution, progressively introducing the OneStream concepts and APIs needed to implement it.
Related Content
Continue with the next guides in this series, or jump to a specific topic:
- The OneStream Data Model — Dimensions, cubes, scenarios, and how OneStream organizes financial data
- Getting Started with Business Rules — The fundamentals of writing Business Rules in OneStream