DBS-C01 Deployment and Migration Practice Question
A company is migrating a 3 TB Oracle database to Amazon RDS for Oracle. The migration uses AWS DMS with ongoing replication. The source database is actively used by applications. After the initial full load, the target RDS instance is in sync. However, during the ongoing replication phase, the replication task fails with an error: 'ORA-1555: snapshot too old.' The DMS task has been set up with a source endpoint that uses the 'Oracle TNS' connection method. The company needs to resolve the issue without stopping the source database. Which action should be taken?
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
✓
Increase the undo retention period in the source Oracle database.
The ORA-1555 error indicates that undo data is overwritten before DMS can read it. Increasing undo retention ensures the snapshot data is available longer. Reducing batch size would not address the undo issue. Increasing logging frequency does not affect undo. Using a different connection method does not solve the underlying undo retention problem.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Change the source endpoint to use the 'Oracle SID' connection method.
Why it's wrong here
Connection method does not affect undo retention.
- ✗
Decrease the batch size of the DMS task.
Why it's wrong here
Batch size affects throughput, not undo retention.
- ✓
Increase the undo retention period in the source Oracle database.
Why this is correct
Longer undo retention keeps snapshot data available for DMS.
- ✗
Increase the frequency of the DMS task's log mining.
Why it's wrong here
Log mining frequency does not affect undo retention.
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