# What a migration costs you

A migration is cheap in money and not free in disruption. Knowing the four costs up front is what stops a run being a surprise to everybody else.

None of them are large. All of them are worth telling people about first.

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## The four costs

| **Cost**                                          | **Detail**                                                                                    |
| ------------------------------------------------- | --------------------------------------------------------------------------------------------- |
| A new page version on every changed page          | This is the safety net, and it is also a lot of versions on a large space.                    |
| Watcher notifications                             | Page watchers may be notified of those versions. On a busy space, tell people before you run. |
| Run time                                          | The tab has to stay open. A large estate with diagram history replay can take hours.          |
| Duplicated content, if you use Keep source macros | The page renders twice until you clean up, and re-running does not remove the duplicates.     |

ℹ️

**Pages that did not change cost nothing.** A page is only saved when its content actually changed, so a re-run over an already-migrated space creates no versions at all.

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## What it does not cost

* Nothing is deleted. Original attachments, preview images and vendor content are read and left in place.
* No content is lost on failure. A macro that fails to convert stays exactly as it was.
* No licence juggling during the run. You can keep both apps installed while you review.

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## A few things that catch people out

* Version churn is the cost people forget to mention to space admins. It is the one that generates complaints.
* Keep source macros is a pilot option, not a production one.
* The run cannot be paused and resumed. Budget the time in one sitting.

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## Related

[Communicating a migrationTelling people first.](https://help.gocapable.com/migration/communicating-a-migration.html)

[How long a migration takesBudgeting the time.](https://help.gocapable.com/migration/how-long-a-migration-takes.html)

[What is never touchedThe reassuring half.](https://help.gocapable.com/migration/what-is-never-touched.html)

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_Cheap, but not invisible._