Oracle Migration with LOBs to RDS
A company is migrating an on-premises Oracle database to Amazon RDS for Oracle. The database has a large table with a BLOB column storing PDF files. Which migration approach minimizes downtime?
Quick Answer
The correct choice is to use AWS Database Migration Service (DMS) with ongoing replication because it directly addresses the need to migrate Oracle databases with LOBs to RDS with minimal downtime. DMS performs a full load of the table, including BLOB columns storing PDFs, while simultaneously capturing and applying ongoing changes from the source, keeping the target RDS instance nearly in sync until cutover. This approach is tested on the AWS Certified Database Specialty DBS-C01 exam as a core strategy for reducing downtime during large-object migrations; a common trap is assuming that export/import or backup restore is faster, but those methods require the source to be offline for the entire duration. Remember that DMS’s change data capture (CDC) is the key to zero-downtime migrations—think "LOB + CDC = low downtime."
⚠ Common exam trap
Many exam-takers assume traditional Oracle tools like Data Pump or RMAN are the best for minimizing downtime, but they fail to recognize that AWS DMS with ongoing replication is specifically designed for near-zero downtime migrations by continuously synchronizing changes.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use AWS Database Migration Service (DMS) with ongoing replication.
AWS DMS with ongoing replication (change data capture) allows you to perform an initial full load of the database while continuously capturing and applying changes from the source Oracle database to the target RDS for Oracle instance. This minimizes downtime because you can cut over to the new database after the initial load and replication lag is near zero, rather than taking the source offline for the entire migration.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use Oracle Data Pump to export the table and import into RDS.
Why it's wrong here
Export/import requires application downtime and does not support ongoing replication.
- ✗
Use Oracle RMAN to back up the database and restore to RDS.
Why it's wrong here
RMAN restore requires a compatible Oracle version and does not support ongoing replication.
- ✗
Export the table without the BLOB column, then import the BLOBs separately.
Why it's wrong here
This approach is complex and still requires downtime for the BLOB data.
- ✓
Use AWS Database Migration Service (DMS) with ongoing replication.
Why this is correct
DMS can perform a full load and then continuously replicate changes to minimize downtime.
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Variation 1. A company is migrating a 5 TB Oracle database to Amazon RDS for Oracle. The database has several large tables with LOB columns. The migration must have minimal downtime. Which approach should be taken?
hard- A.Use Oracle GoldenGate to replicate data to RDS.
- ✓ B.Use AWS DMS with LOB support and ongoing replication from Oracle to RDS.
- C.Use Oracle Data Pump to export the database and import into RDS.
- D.Copy the database files to Amazon S3 and use the rdsadmin.rds_restore_from_s3 procedure.
Why B: AWS DMS with LOB support and ongoing replication (change data capture, CDC) is the correct approach because it enables a near-zero downtime migration by continuously replicating changes from the source Oracle database to Amazon RDS for Oracle after an initial full load. DMS handles large LOB columns efficiently using its 'Full LOB mode' or 'Limited LOB mode' settings, which are critical for tables with LOB data. The combination of full load + CDC ensures minimal downtime, as the target remains synchronized until cutover.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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