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.