I have upgraded lots of SQL Servers from one version to the next, and for the most part, the process has been smooth. That's not always the case, and there have been some long nights where the Operations staff had to scramble to fix things, script out old logins, call Microsoft support, and perform various data exports and imports to get a new instance running. I've been a part of quite a few of those teams.

Most of my upgrades were with relatively small databases, at least small for that time period. However, I have upgraded a few "large" databases in the past. We had a 400GB database on SQL Server 6.5 in 1999 that was a challenge to move to SQL Server 7. I also upgraded an 800GB database in 2001 from 6.5 to 2000 for our Financial team, which involved a lot of stress.

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