Migrating large TB of Data from Teradata to Oracle (On-Prem & OCI Autonomous): A Step-by-Step Guide

Migrating large datasets from Teradata to Oracle requires careful planning, efficient data transfer strategies, and thorough validation to ensure data integrity. In this guide, we outline a step-by-step approach to migrating large volume TB of data with minimal downtime and maximum efficiency, covering both on-premises Oracle databases and Oracle Cloud Infrastructure (OCI) Autonomous Database.

Current blog you are reading is more of strategical high-level steps,

please see below link to get more into technical side -

https://www.aitechblog.blog/post/teradata-to-oracle-on-prem-oci-autonomous-migration-guide

Step 1: Assess the Current Teradata Environment

Before migration, conduct a thorough assessment of the Teradata environment:

• Identify database schema, table structures, and indexes.

• Assess data volume and growth trends.

• Evaluate dependencies, stored procedures, and views that need migration.

• Identify performance bottlenecks and data consistency issues.

Step 2: Prepare the Oracle Target Environment

Ensure that the Oracle environment is ready to accommodate the migration:

• Install and configure Oracle Database (preferably Oracle 19c or later for on-premises or OCI Autonomous Database for cloud migration).

• Set up tablespaces, partitions, and indexes based on Teradata structures.

• Optimize storage capacity to handle 160TB efficiently.

• Configure parallelism and performance tuning parameters.

Step 3: Choose a Data Migration Strategy

There are multiple approaches to migrating data from Teradata to Oracle. Select the best-fit approach based on your requirements:

1. Direct Migration via Oracle SQL Loader

• Export Teradata data using FastExport.

• Convert data to CSV or flat files.

• Use Oracle SQL Loader or External Tables to ingest data into Oracle.

• Works for both on-prem and OCI Autonomous Database.

• Pros: Simple and effective for structured data.

• Cons: Can be slow for massive datasets.

2. Parallel Data Load with Oracle Data Pump

• Export data from Teradata in CSV format.

• Use Oracle Data Pump (impdp) for parallel data import.

• Works for both on-prem and OCI Autonomous Database.

• Pros: Faster load times due to parallel execution.

• Cons: Requires pre-created schema in Oracle.

3. ETL-Based Migration Using Informatica or Apache NiFi

• Use ETL tools (e.g., Informatica, Talend, NiFi) for data transformation and migration.

• Supports both on-prem and OCI Autonomous Database.

• Pros: Best for complex transformations and data cleansing.

• Cons: Requires licensing for ETL tools.

4. Real-Time Streaming via Oracle GoldenGate

• Use Oracle GoldenGate for real-time replication.

• Supports CDC (Change Data Capture) for near-zero downtime migration.

• Works for both on-prem and OCI Autonomous Database.

• Pros: Best for minimal downtime and continuous data synchronization.

• Cons: Additional setup complexity and licensing costs.

Step 4: Data Extraction from Teradata

Perform a controlled data extraction using FastExport or BTEQ:

.EXPORT FILE = 'data_extract.csv'; SELECT * FROM TeradataTable; .EXPORT RESET;

• Optimize extraction using multithreading and parallel sessions.

• Break down large tables into smaller chunks using partitioning.

Step 5: Data Transformation & Cleansing

• Convert Teradata data types to Oracle-compatible types (e.g., BYTEINT → NUMBER).

• Normalize NULL values, date formats, and string encodings.

• Validate and cleanse data to remove inconsistencies.

Step 6: Load Data into Oracle (On-Prem & OCI Autonomous Database)

Use SQL Loader or Data Pump to import data into Oracle:

sqlldr userid=username/password control=control_file.ctl log=logfile.log

For OCI Autonomous Database, leverage Oracle Object Storage for loading:

BEGIN DBMS_CLOUD.COPY_DATA( table_name => 'TARGET_TABLE', credential_name => 'OBJ_STORAGE_CRED', file_uri_list => 'https://objectstorage.us-ashburn-1.oraclecloud.com/.../data_extract.csv', format => json_object('skipheaders' value '1') ); END; /

• Use parallel processing for faster loads.

• Implement batch inserts to minimize logging overhead.

• Ensure proper indexing and partitioning for optimized performance.

Step 7: Validate Data Integrity

Perform thorough validation post-migration:

• Row count comparison between Teradata and Oracle.

• Data sampling checks to verify accuracy.

• Automated validation scripts to check NULLs, duplicates, and mismatches.

• Run performance tests on queries in Oracle to match Teradata execution.

Step 8: Migrate Stored Procedures & Business Logic

Convert Teradata stored procedures (written in BTEQ or SQL) to Oracle PL/SQL.

• Rewrite CASE statements, SET operations, and loops.

• Validate triggers, views, and constraints in Oracle.

Step 9: Implement Incremental Data Sync & Cutover

• Use CDC (Change Data Capture) with Oracle GoldenGate or custom scripts.

• Migrate only delta changes after initial load.

• Perform final testing and performance tuning.

• Plan a cutover window and switch applications to Oracle.

Step 10: Post-Migration Optimization

• Rebuild indexes and statistics for better query performance.

• Implement backup strategies for Oracle.

• Monitor query execution times and fine-tune performance.

• Ensure application compatibility with the new Oracle database.

Conclusion

Migrating Large volume TB of data from Teradata to Oracle (On-Prem & OCI Autonomous Database) is a complex process that requires a structured approach. By using parallel processing, data transformation, real-time sync, and validation techniques, organizations can ensure a seamless and efficient migration with minimal downtime. Choosing the right migration strategy based on performance, business needs, and infrastructure will lead to a successful data transition.