what is a rolling restart

can someone tell me please, what this means

thank you

They're like rolling blackouts by the power company, only Linden Lab does it, and it involves restarting the sim you're standing in. Almost always during an event you're running and/or attending.

You're usually given a warning, and then logged out of sl if you don't get out fast enough.

YMMV.

They restart each sim, one by one or in groups, usually for the purposes of deploying new server software or repairing malfunctions. It used to be they had to take the entire grid offline all at once to do these things. Rolling restarts are a considerable improvement.

Just what Chosen said. You'll see a blue window pop up on your monitor screen giving a time warning. Usually it is a five minute warning to leave the sim. You can either teleport to another sim(check Map first to make sure that one isn't offline) or just Quit for a short while.

You can always get that load of laundry done until you log back on, lol.

The "rolling" comes from them taking the servers offline in batches. They used to do this based on the location of the sim in the world, so the restarts would roll like a wave across the world.
Now it's more random which server is restarted when, but the "rolling restart" term is still used, referring to restarting every server in turn (or at least a large part) for a general update.

When you've drunk too much because it's close to Christmas and you fall over at the Pub.You get up and roll back to the bar for a refill. That's a rolling restart!!

thank you very much, I have been in a sim when the estate manager restarted the sim, I was not sure it this was the same thing