Oracle 5.0 Reference Manual page 2972

privilege to administrators and not to normal users (who should not need it), an administrator can
connect to the server and use
number of unprivileged clients are connected. See
The maximum number of connections MySQL can support depends on the quality of the thread library
on a given platform, the amount of RAM available, how much RAM is used for each connection, the
workload from each connection, and the desired response time. Linux or Solaris should be able to
support at 500 to 1000 simultaneous connections routinely and as many as 10,000 connections if you
have many gigabytes of RAM available and the workload from each is low or the response time target
undemanding. Windows is limited to (open tables × 2 + open connections) < 2048 due to the Posix
compatibility layer used on that platform.
Increasing
open-files-limit
Postinstallation
by MySQL.
C.5.2.8.
Out of memory
If you issue a query using the
means that
mysql: Out of memory at line 42, 'malloc.c'
mysql: needed 8136 byte (8k), memory in use: 12481367 bytes (12189k)
ERROR 2008: MySQL client ran out of memory
To remedy the problem, first check whether your query is correct. Is it reasonable that it should return
so many rows? If not, correct the query and try again. Otherwise, you can invoke
[268]
quick
result set, which places less of a load on the client (but more on the server).
C.5.2.9.
MySQL server has gone away
This section also covers the related
The most common reason for the
and closed the connection. In this case, you normally get one of the following error codes (which one
you get is operating system-dependent).
Error Code
CR_SERVER_GONE_ERROR
CR_SERVER_LOST
By default, the server closes the connection after eight hours if nothing has happened. You can change
the time limit by setting the
"Server System
If you have a script, you just have to issue the query again for the client to do an automatic
reconnection. This assumes that you have automatic reconnection in the client enabled (which is the
default for the
Some other common reasons for the
• You (or the db administrator) has killed the running thread with a
command.
kill
• You tried to run a query after closing the connection to the server. This indicates a logic error in the
application that should be corrected.
• A client application running on a different host does not have the necessary privileges to connect to
the MySQL server from that host.
Common Errors When Using MySQL Programs
SHOW PROCESSLIST
[417]
Notes", for how to raise the operating system limit on how many handles can be used
mysql
does not have enough memory to store the entire query result:
mysql
option. This causes it to use the
MySQL server has gone away
[2942]
[2942]
wait_timeout
Variables".
command-line client).
mysql
to diagnose problems even if the maximum
Section 13.7.5.27,
may be necessary. Also see
client program and receive an error like the following one, it
mysql_use_result()
Lost connection to server during query
Description
The client couldn't send a question to the server.
The client didn't get an error when writing to the server, but it
didn't get a full answer (or any answer) to the question.
[506] variable when you start mysqld. See
MySQL server has gone away
2952
"SHOW PROCESSLIST
Section 2.20.1.4, "Linux
with the
mysql
C API function to retrieve the
error.
error is that the server timed out
Section 5.1.4,
error are:
statement or a
KILL mysqladmin
Syntax".
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