MySQL

This ID uniquely identify each server instance in the community of replication partners.

Each thread that does a sequential scan allocates a buffer of this size for each table it scans. If you do many sequential scans, you may want to increase this value.

The size of the buffer that is used for joins that do not use indexes and thus perform full table scans. Normally, the best way to get fast joins is to add indexes. Increase the value of join_buffer_size to get a faster full join when adding indexes is not possible. One join buffer is allocated for each full join between two tables. For a complex join between several tables for which indexes are not used, multiple join buffers might be necessary.

Index blocks for MyISAM tables are buffered and are shared by all threads. key_buffer_size is the size of the buffer used for index blocks. The key buffer is also known as the key cache. The maximum allowable setting for key_buffer_size is 4GB. The effective maximum size might be less, depending on your available physical RAM and per-process RAM limits imposed by your operating system or hardware platform. Increase the value to get better index handling (for all reads and multiple writes) to as much as you can afford. Using a value that is 25% of total memory on a machine that mainly runs MySQL is quite common. However, if you make the value too large (for example, more than 50% of your total memory) your system might start to page and become extremely slow. MySQL relies on the operating system to perform filesystem caching for data reads, so you must leave some room for the filesystem cache. Consider also the memory requirements of other storage engines.

The number of seconds the server waits for activity on a non-interactive connection before closing it. This timeout applies only to TCP/IP and Unix socket file connections, not to connections made via named pipes, or shared memory.

The number of seconds the server waits for activity on an interactive connection before closing it. An interactive client is defined as a client that uses the CLIENT_INTERACTIVE option to mysql_real_connect(). See also wait_timeout.

The maximum number of simultaneous connections allowed to any given MySQL account. A value of 0 means “no limit.” Before MySQL 5.0.3, this variable has only global scope. Beginning with MySQL 5.0.3, it also has a read-only session scope. The session variable has the same value as the global variable unless the current account has a non-zero MAX_USER_CONNECTIONS resource limit. In that case, the session value reflects the account limit.

Don't cache results that are larger than this number of bytes. The default value is 1MB.

Set the SQL mode. This option was added in 3.23.41.

Options that begin with --ssl specify whether to allow clients to connect via SSL and indicate where to find SSL keys and certificates.