Several parameters of MySQL

Back_log:

The operating system maintains a listening queue, which is done before the MySQL thread is connected

If you have a lot of connections and there are connection refused error prompts, adding this value is certainly true.

Skip-networking:

This is not listening for TCP/IP connections. This time can only be connected via socket or named PIP

Max_connect_errors:

The number of times an error is allowed for each host connection, and if this value is reached, the host cannot be connected unless the flush hosts command is used or the database is restarted. An incorrect password or other error can cause the value to increase. This time you can look at the Aborted_connects state variables to verify the connection changes.

Binlog_cache_size

The binary log cache, if the transaction with large, and many statements, increase the value can increase performance, when the transaction commit will be refreshed in the binary log. If the transaction size is larger than this value, the temporary table on the hard disk is used. Can degrade performance

Read_buffer_size

For the memory used by the full table scan,

Read_rnd_buffer_size:

When reading rows into sorted order after a sort, the rows are read through this buffer to avoid disk seeks. For using the ORDER BY statement , you should increase the value.

Sort_buffer_size

It is advantageous for order by and group by queries, which use temporary tables on the disk if sorted data is larger than the sort buffer.

Join_buffer_size

Used primarily in join queries where no indexes are used. You can observe select_full_join to determine the number of such queries

Thread_concurrency:

CPUs * (2..4) allows thread system to have n threads running at the same time

Ft_min_word_len:

Use of the prefix index length for full text search

thread_stack=240k

The size of the thread stack, which is always saved when the connection is established

Tmpdir =/usr/local/mysql/data

Store temporary files, such as: large sorts,temporary tables file