Variables configure server resources and can be used to optimize
the server settings to suit the hardware of the host computer, and to
allocate resources for improved performance. For example, the
max_connections specifies the maximum number
of clients that can be connected to the server at any one time.
When choosing a value for a server variable, you need to think
carefully about the nature of your application and your clients. For
example, when setting the
max_connections variable, you need to remember
that clients can include application web pages that interact with the
database. This variable affects the number of people who can
concurrently load the database-enabled web pages; each request to load
such a page counts as a separate connection. Of course, these
connections are short, typically lasting only a few
seconds while the page is generated and served to the web
Some of the more important variables control how memory and
files are managed. MySQL databases are stored in files in the data
directory, and the server needs to open and close these files.
However, opening and closing files is a relatively slow operation, so
the fewer times we need to do this, the better. The MySQL server
table_cache specifies the maximum number of
tables that can be open at once. The larger this number, the fewer
times we need to close open files and open closed ones.
You also need to consider how the
max_connections value influences the value you choose ...