Re-platforming Oracle Databases to Microsoft SQL Server
For organizations standardized on the Microsoft stack, moving from Oracle to SQL Server can simplify skills, tools and licensing. This paper outlines a proven method for converting schema, PL/SQL logic and data with minimal downtime.
1Challenge
- Rising Oracle costs while most of the application and BI estate already runs on Microsoft technologies.
- Split skills: separate Oracle and SQL Server teams, tools and processes double the operational effort.
- Complex procedural code: packages, triggers and PL/SQL features have no direct one-to-one match in T-SQL.
- Downtime limits: business-critical applications can only accept short outage windows.
2Solution
Assess
Run Microsoft's SQL Server Migration Assistant (SSMA) for Oracle to inventory objects and estimate conversion complexity, then identify application SQL embedded in code.
Convert schema & code
Convert automatically with SSMA, then refactor by hand where it can't: packages become schemas plus procedures, autonomous transactions and hierarchical queries are re-designed.
Migrate data
Bulk-load history, then keep the target current with change-data-capture (for example Qlik Replicate, Oracle GoldenGate or Azure DMS) until cut-over.
Validate
Reconcile row counts and checksums, run parallel functional tests and compare performance against baselines.
Cut over & optimize
Switch over in a rehearsed window, then tune indexes, statistics and Query Store, and set up Always On availability groups.
| Oracle | SQL Server |
|---|---|
| NUMBER(p,s) | NUMERIC/DECIMAL(p,s), INT, BIGINT |
| VARCHAR2 / NVARCHAR2 | VARCHAR / NVARCHAR |
| DATE / TIMESTAMP | DATETIME2 |
| CLOB / BLOB | VARCHAR(MAX) / VARBINARY(MAX) |
| SEQUENCE | SEQUENCE or IDENTITY |
| PL/SQL package | Schema + stored procedures/functions |
| Data Guard | Always On availability groups |
3Results
One platform
A unified Microsoft data stack simplifies tools, skills and support.
Licensing efficiency
Oracle support costs are retired and SQL Server editions are matched to each workload's needs.
Minimal downtime
CDC-based sync keeps cut-over to a planned, short window.
BI integration
Native integration with Power BI, SSIS and Azure services.
This white paper is general, educational guidance. Results depend on each organization's environment, contracts and scope. Product names are trademarks of their respective owners and are used for identification only.
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