The MySQL Server 5.8.1 Setting Up Multiple Data Directories .............................................................................. 1147 5.8.2 Running Multiple MySQL Instances on Windows ........................................................... 1148 5.8.3 Running Multiple MySQL Instances on Unix .................................................................. 1151 5.8.4 Using Client Programs in a Multiple-Server Environment ................................................ 1152 5.9 Debugging MySQL .................................................................................................................. 1153 5.9.1 Debugging a MySQL Server ......................................................................................... 1153 5.9.2 Debugging a MySQL Client .......................................................................................... 1159 5.9.3 The LOCK_ORDER Tool .............................................................................................. 1159 5.9.4 The DBUG Package ..................................................................................................... 1165 MySQL Server ( mysqld ) is the main program that does most of the work in a MySQL installation. This chapter provides an overview of MySQL Server and covers general server administration: •Server configuration •The data directory, particularly the  mysql  system schema •The server log files •Management of multiple servers on a single machine •Chapter 6,  Security •Chapter 7,  Backup and Recovery •Chapter 17,  Replication For additional information on administrative topics, see also: mysqld  is the MySQL server. The following discussion covers these MySQL server configuration topics: 5.1 The MySQL Server •Startup options that the server supports. You can specify these options on the command line, through configuration files, or both. •Server system variables. These variables reflect the current state and values of the startup options, some of which can be modified while the server is running. •Server status variables. These variables contain counters and statistics about runtime operation. •How to set the server SQL mode. This setting modifies certain aspects of SQL syntax and semantics, for example for compatibility with code from other database systems, or to control the error handling for particular situations. •How the server manages client connections. •Configuring and using IPv6 and network namespace support. •Configuring and using time zone support. •Using resource groups. •Server-side help capabilities. •Capabilities provided to enable client session state changes. •The server shutdown process. There are performance and reliability considerations depending on the type of table (transactional or nontransactional) and whether you use replication. 638