Large SQL Server tables with growing identity columns can run out of integer capacity and require changing the datatype from INT to BIGINT – but a direct ALTER TABLE can cause extensive downtime due to index rebuilds and heavy logging. This session walks through a real-world approach used on a 500 GB, ~900 million row table to plan and execute the change with minimal production impact. You’ll learn techniques for creating a replica table with the new datatype, synchronizing data using ETL processes, using object-level restore to stage the change, and performing a final cut-over during a short maintenance window. Practical tips on testing, data consistency verification, and reducing downtime will help you safely implement datatype changes on high-volume systems.