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tables_cache and open_files Server settings
Posted by: Erin ONeill
Date: June 30, 2005 11:38AM

I'm trying to tweak a MySQL server to get blazing performance out of it. I've been reading books and online. I think I have a handle on some of the formulas for determining values. Now I need more information about two settings and I can't seem to find the info (perhaps my cold has frozen my brain?).

It's my understanding that the tables cache setting is this formula:
max_connections * avg.-num-tables-in-join <= open_files

open_files is 3010. max_connections is 400, table joins tend to be 3-4 tables. So 3*400 = 1200, which is lower than 3010. I set my server to this parameter and the server screamed. I went on to slow queries. Then the server crashed with the error: too many open files!!

Why didn't MySQL close files after the 3010 limit was reached? Why did it crash, rather than close files.

If the formula I have is wrong -- does anyone have a more correct one?

I do know that cache tables really speeds up the server - I just can't have it crashing and want to prevent that.

thanks all
erin

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