Workloads rarely live alone. A migration that moves one component without knowing what it talks to will break something at cutover. A dependency map is how you avoid that.
Every application in a real estate is part of a web. It calls databases, message queues, identity providers, file shares, third party services and other applications, and many of those connections are undocumented, known only to whoever built them years ago. A migration that moves a workload without understanding this web will sever a connection nobody remembered, and the failure will surface at the worst possible moment, during or just after cutover. A dependency map is the artefact that prevents this, and building it is the foundation of a safe migration.
It is one of the core inputs to the wave planning described in our pillar guide, The Complete Guide to Oracle Cloud Migration in 2026.
| Dependency type | Example | Why it matters for migration |
|---|---|---|
| Data | App reads from a database | Latency if separated across regions |
| Integration | App calls an API or queue | Breaks if endpoint changes |
| Identity | App authenticates via a directory | Login fails if not migrated together |
| Network | Firewall rules and routes | Connectivity lost if not recreated |
| Shared service | Logging, monitoring, file shares | Silent gaps if forgotten |
The dependencies that cause incidents are never the ones in the architecture diagram. They are the cron job that copies a file, the hard coded address in a config, the integration built for a project years ago that nobody decommissioned. These are invisible to a paper review and only surface through observation of real traffic, which is why dependency mapping has to combine documentation with measurement.
No single source is complete. Documentation is stale, traffic observation misses infrequent connections, and owners forget. The reliable map is the union of all three, reconciled into one picture that the wave plan can build on.
The point of the map is not the diagram, it is the decision it enables. Workloads that depend heavily on each other should move together in the same wave, so their connections stay intact, while loosely coupled workloads can move independently. This grouping is the heart of wave planning, covered in How to Plan an OCI Migration Wave, and a good map makes good grouping almost mechanical.
A dependency map is the antidote to several of the recurring errors catalogued in Common OCI Migration Mistakes to Avoid. It prevents the broken integration at cutover, it informs the rollback plan by showing what a failed wave affects, and it surfaces the chatty connections that would otherwise generate surprise egress charges once separated.
A complete dependency map does double duty after the migration. The connections that turn out to lead nowhere, the integrations to systems already retired, the data feeds nobody consumes, are candidates for decommissioning rather than migration. Moving them wastes effort and clutters the new estate, so a good map shrinks the migration as well as de risking it. This pairs naturally with the validation work in Post Migration Validation on OCI, which confirms that the connections you kept actually work.
A dependency map built for a migration is too valuable to abandon once the move is done. Kept current, it becomes the reference for change management, incident response and future architecture decisions, because it answers the question that causes most outages, namely what depends on this thing I am about to change. The discipline of maintaining it is part of running an estate well rather than just moving one, which is where ongoing management earns its place.
Dependency mapping is part of the assessment, not a separate project, and our OCI Implementation and Migration practice builds it into every engagement using a combination of tooling and interviews. The map it produces is the artefact the whole programme leans on, from wave planning through rollback design to validation, which is why we treat it as the first deliverable rather than a nice to have.
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