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Re: Server just hanging (Copying to tmp table)
Posted by: Daniel Nichter
Date: August 31, 2005 07:15PM

An interesting idea. Though, if open files were the problem, you'd think the status of the thread would be "Copying to tmp table on disk" instead. Perhaps MySQL is switching from a memory table to a disk table, can't get the file handle, then freezes and so the thread status doesn't get updated. For this to be the case, table_cache would have to be set to ulimit -n for the system and be at 100% usage. In my case it was I believe (I know it was set to 1028 for some weird reason, and I know the server hit 100% table cache usage). Thomas and Shawn: Is this true for your servers too?

In Thomas's last post of a mysqlreport report, his table_cache was only 1,000 though, and the problem still occurred (Open 1.00k of 1000 %Cache: 100.00); that would seem to dismiss or change the theory. Perhaps it's just a general problem with 100% table cache usage and temp tables, though I don't see how the two are related if not by open file limits and disk tmp tables.

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