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Assess and plan the migration by inventorying SQL Server objects, identifying compatibility issues, evaluating dependencies, and setting clear goals using tools like Oracle SQL Developer’s Migration Workbench. 2. Convert schema and objects by translating data types (e.g., VARCHAR(MAX) to CLOB, DATETIME to TIMESTAMP), rewriting T-SQL to PL/SQL, and using tools like Oracle SQL Developer or AWS Schema Conversion Tool with manual review. 3. Migrate and validate data using methods such as Oracle SQL Developer, Oracle GoldenGate, ETL tools, or CSV import, while ensuring data integrity through row counts, checksums, and attention to encoding, date/time, and precision issues. 4. Update application code by changing connection strings to Oracle JDBC or ODP.NET, replacing SQL Server-specific syntax (e.g., TOP with ROWNUM, GETDATE() with SYSDATE, ISNULL() with NVL()), and conducting functional, performance, and security testing. 5. Handle ongoing maintenance by replacing SQL Server Agent with Oracle DBMS_SCHEDULER, setting up monitoring via Oracle Enterprise Manager or scripts, and training DBAs and developers on Oracle practices, ensuring a successful transition that combines automation with meticulous manual refinement.

Migrating from SQL Server to Oracle is a common requirement when organizations shift their database platforms due to licensing, scalability, or integration needs. While the process isn't trivial, it can be managed effectively with proper planning and tools. Here’s a practical guide to help you through the key steps.

1. Assess and Plan the Migration

Before any data moves, understand what you're migrating:

• Inventory your SQL Server environment: List databases, tables, views, stored procedures, functions, triggers, jobs, and linked servers.
• Identify compatibility issues: Oracle and SQL Server differ in SQL syntax, data types, and procedural logic (T-SQL vs PL/SQL).
• Evaluate dependencies: Check application connections, reporting tools (like SSRS), and ETL processes (e.g., SSIS).
• Set migration goals: Full migration? Phased approach? Downtime window?

Tip: Use Oracle’s SQL Developer with its Migration Workbench — it helps analyze SQL Server objects and suggests Oracle equivalents.

2. Convert Schema and Objects

Schema migration requires translating SQL Server DDL to Oracle-compatible syntax.

Key differences to handle:

• Data types:
  • VARCHAR(MAX) → CLOB or VARCHAR2(4000)
  • NVARCHAR → NVARCHAR2
  • DATETIME → TIMESTAMP
  • IDENTITY(1,1) → Use SEQUENCE TRIGGER or IDENTITY columns (Oracle 12c )
• Primary/Foreign Keys, Indexes, Constraints: These usually convert directly, but naming and syntax may vary.
• Stored Procedures & Functions:
  • T-SQL → PL/SQL rewrite required.
  • Example: BEGIN...END, PRINT, @@IDENTITY have different equivalents in Oracle.

Tools to help:

• Oracle SQL Developer (Free): Connects to SQL Server, migrates schema automatically, and maps data types.
• AWS Schema Conversion Tool (SCT): Useful for complex logic, converts some T-SQL to PL/SQL.
• Manual review is still essential — automated tools don’t catch everything.

Pro tip: Start with a small subset of tables and logic to test the conversion flow before scaling.

3. Migrate and Validate Data

Once the schema is in Oracle, move the data.

Options:

• Oracle SQL Developer: Can copy data directly from SQL Server to Oracle over a linked connection.
• Oracle GoldenGate: For real-time, minimal-downtime migration (enterprise use).
• ETL Tools: Use Informatica, Talend, or SSIS with Oracle connectors.
• CSV Export/Import: Simple but slow; use for small datasets.

Best practices:

• Migrate in batches if possible.
• Verify row counts and checksums post-migration.
• Handle data encoding (especially for Unicode/UTF-8).

Watch for date/time and decimal precision issues — they often cause silent data truncation.

4. Update Application Code and Test

Most applications assume SQL Server-specific syntax or use ADO.NET, which may need changes.

Common changes:

• Connection strings → Use Oracle JDBC (Java) or ODP.NET (C#)
• SQL queries:
  • TOP → ROWNUM or FETCH FIRST
  • GETDATE() → SYSDATE
  • ISNULL() → NVL() or COALESCE()
• Pagination, auto-increment logic, and transaction handling may need updates.

Testing checklist:

• Functional testing: Do all queries return correct results?
• Performance testing: Are indexes and execution plans optimal?
• Security: Roles, users, and privileges recreated in Oracle?

5. Handle Ongoing Maintenance

After migration:

• Replace SQL Server Agent jobs with Oracle Scheduler (DBMS_SCHEDULER).
• Set up Oracle Enterprise Manager or use scripts for monitoring.
• Train DBAs and developers on Oracle tools and practices.

Migrating from SQL Server to Oracle involves more than just moving data — it’s about adapting logic, syntax, and operations. Use Oracle’s free tools to simplify the process, but expect to manually refine complex procedures and application code. Start small, test thoroughly, and involve both DBAs and developers early.

Basically, it's a mix of automation and careful manual work — not rocket science, but easy to get wrong if rushed.

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