ANSWER

What happens to historical data when the legacy system is shut down?

Reviewed August 1, 2026.

Shutting down a legacy system does not shut down the obligations over its data. Before cutover, historical data needs three written answers: what legal and contractual retention requires you to keep (and for how long), where it will remain accessible for queries and audits without depending on the old application, and what will be disposed of with a record. Migrating everything into the new system is rarely the answer — archiving with read access usually costs less and proves more.

Step by step

• Inventory the data by obligation: tax, labor, contractual and data-protection law — each with its retention period.
• Separate live data (what the new process needs) from historical data (queries and proof).
• Define the read destination: a structured export with a data dictionary and a named owner.
• Test the queries before cutover: auditors ask for samples, not goodwill.
• Record the disposal of what passed retention — deleting is also an obligation, not just a right.

How an agent does this

In an AgenticosCore Legacy Exit, the destination of historical data goes into the cutover plan — the evidence pack and the decommissioning checklist: retention mapped, read destination tested and disposal recorded. The agent taking over the process does not inherit the whole database — it uses the live data and keeps an auditable path to the rest.