1.
SQL Syntax Differences
- Oracle uses PL/SQL, while BigQuery uses standard SQL.
- Key differences in functions, procedures, windowing functions, and error handling often require manual rewriting.
2.
Stored Procedures & Packages
- Oracle’s stored procedures, packages, and triggers are deeply embedded in workflows.
- BigQuery has limited support for procedural logic and doesn’t support packages like Oracle.
3.
ETL/ELT Reengineering
- ETL processes built with Oracle-specific tools (e.g., Oracle Data Integrator) must be re-architected using tools compatible with BigQuery (e.g., Dataflow, Cloud Composer, dbt).
4.
Data Type Mismatches
- Differences in data types (e.g., NUMBER, DATE, CLOB) between Oracle and BigQuery can cause data fidelity issues during migration.
5.
Performance Tuning Shift
- Oracle relies on indexes, partitions, and hints, while BigQuery is serverless and relies on query optimization and table partitioning strategies.
- Performance tuning paradigms must be relearned.
6.
Security and Access Control
- Oracle uses role-based access control and fine-grained access policies, which may not map 1:1 to BigQuery’s IAM model.
- Requires redesign of data governance policies.
7.
Migration of Historical Data
- Large volumes of data, especially if not well-partitioned, can be costly and time-consuming to move.
- May require staging in Google Cloud Storage and batch load jobs.
8.
Change Management & User Training
- Analysts and developers accustomed to Oracle tools need training in BigQuery and associated cloud-native tools.
- Business users may also need to adapt to new reporting workflows (e.g., from Oracle BI to Looker).
9.
Integration with Legacy Systems
- Oracle often integrates tightly with legacy ERP systems and custom apps.
- BigQuery may require middleware or APIs to maintain similar integrations.
10.
Cost Management
- BigQuery uses pay-per-query pricing, which is very different from Oracle’s licensing model.
- Lack of understanding of cost controls (e.g., materialized views, partitions, byte limits) can lead to unexpected costs.