This statement provides status information on essential parameters of the slave threads. It requires either the SUPER or REPLICATION CLIENT privilege.

If you issue this statement using the mysql client, you can use a \G statement terminator rather than a semicolon to obtain a more readable vertical layout:

*************************** 1. row ***************************
             Slave_IO_State: Waiting for master to send event
                Master_Host: localhost
                Master_User: root
                Master_Port: 3306
              Connect_Retry: 3
            Master_Log_File: gbichot-bin.005
        Read_Master_Log_Pos: 79
             Relay_Log_File: gbichot-relay-bin.005
              Relay_Log_Pos: 548
      Relay_Master_Log_File: gbichot-bin.005
           Slave_IO_Running: Yes
          Slave_SQL_Running: Yes
                 Last_Errno: 0
               Skip_Counter: 0
        Exec_Master_Log_Pos: 79
            Relay_Log_Space: 552
            Until_Condition: None
              Until_Log_Pos: 0
         Master_SSL_Allowed: No
      Seconds_Behind_Master: 8

The following list describes the fields returned by SHOW SLAVE STATUS. For additional information about interpreting their meanings, see Section, “Checking Replication Status”.

  • Slave_IO_State

    A copy of the State field of the SHOW PROCESSLIST output for the slave I/O thread. This tells you what the thread is doing: trying to connect to the master, waiting for events from the master, reconnecting to the master, and so on. For a listing of possible states, see Section 8.14.6, “Replication Slave I/O Thread States”. For versions of MySQL prior to 5.0.12, it is necessary to check this field for connection problems. In those versions, the thread could be running while unsuccessfully trying to connect to the master; only this field makes you aware of the problem. The state of the SQL thread is not copied because it is simpler. If it is running, there is no problem; if it is not, you can find the error in the Last_Error field (described later).

  • Master_Host

    The master host that the slave is connected to.

  • Master_User

    The user name of the account used to connect to the master.

  • Master_Port

    The port used to connect to the master.

  • Connect_Retry

    The number of seconds between connect retries (default 60). This can be set with the CHANGE MASTER TO statement or --master-connect-retry option.

  • Master_Log_File

    The name of the master binary log file from which the I/O thread is currently reading.

  • Read_Master_Log_Pos

    The position in the current master binary log file up to which the I/O thread has read.

  • Relay_Log_File

    The name of the relay log file from which the SQL thread is currently reading and executing.

  • Relay_Log_Pos

    The position in the current relay log file up to which the SQL thread has read and executed.

  • Relay_Master_Log_File

    The name of the master binary log file containing the most recent event executed by the SQL thread.

  • Slave_IO_Running

    Whether the I/O thread is started and has connected successfully to the master. Internally, the state of this thread is represented by one of the following three values:

    • MYSQL_SLAVE_NOT_RUN. The slave I/O thread is not running. For this state, Slave_IO_Running is No.

    • MYSQL_SLAVE_RUN_NOT_CONNECT. The slave I/O thread is running, but is not connected to a replication master. For this state, Slave_IO_Running depends on the server version as shown in the following table.

      MySQL VersionSlave_IO_Running
      4.1 (4.1.13 and earlier); 5.0 (5.0.11 and earlier)Yes
      4.1 (4.1.14 and later); 5.0 (5.0.12 and later)No
    • MYSQL_SLAVE_RUN_CONNECT. The slave I/O thread is running, and is connected to a replication master. For this state, Slave_IO_Running is Yes.

  • Slave_SQL_Running

    Whether the SQL thread is started.

  • Replicate_Do_DB, Replicate_Ignore_DB

    The lists of databases that were specified with the --replicate-do-db and --replicate-ignore-db options, if any.

  • Replicate_Do_Table, Replicate_Ignore_Table, Replicate_Wild_Do_Table, Replicate_Wild_Ignore_Table

    The lists of tables that were specified with the --replicate-do-table, --replicate-ignore-table, --replicate-wild-do-table, and --replicate-wild-ignore-table options, if any.

  • Last_Errno, Last_Error

    The error number and error message returned by the most recently executed statement. An error number of 0 and message of the empty string mean no error. If the Last_Error value is not empty, it also appears as a message in the slave's error log. For example:

    Last_Errno: 1051
    Last_Error: error 'Unknown table 'z'' on query 'drop table z'

    The message indicates that the table z existed on the master and was dropped there, but it did not exist on the slave, so DROP TABLE failed on the slave. (This might occur, for example, if you forget to copy the table to the slave when setting up replication.)


    When the slave SQL thread receives an error, it reports the error first, then stops the SQL thread. This means that there is a small window of time during which SHOW SLAVE STATUS shows a nonzero value for Last_Errno even though Slave_SQL_Running still displays Yes.

  • Skip_Counter

    The current value of the sql_slave_skip_counter system variable. See Section, “SET GLOBAL sql_slave_skip_counter Syntax”.

  • Exec_Master_Log_Pos

    The position in the current master binary log file to which the SQL thread has read and executed, marking the start of the next transaction or event to be processed. You can use this value with the CHANGE MASTER TO statement's MASTER_LOG_POS option when starting a new slave from an existing slave, so that the new slave reads from this point. The coordinates given by (Relay_Master_Log_File, Exec_Master_Log_Pos) in the master's binary log correspond to the coordinates given by (Relay_Log_File, Relay_Log_Pos) in the relay log.

  • Relay_Log_Space

    The total combined size of all existing relay log files.

  • Until_Condition, Until_Log_File, Until_Log_Pos

    The values specified in the UNTIL clause of the START SLAVE statement.

    Until_Condition has these values:

    • None if no UNTIL clause was specified

    • Master if the slave is reading until a given position in the master's binary log

    • Relay if the slave is reading until a given position in its relay log

    Until_Log_File and Until_Log_Pos indicate the log file name and position that define the coordinates at which the SQL thread stops executing.

  • Master_SSL_Allowed, Master_SSL_CA_File, Master_SSL_CA_Path, Master_SSL_Cert, Master_SSL_Cipher, Master_SSL_Key

    These fields show the SSL parameters used by the slave to connect to the master, if any.

    Master_SSL_Allowed has these values:

    • Yes if an SSL connection to the master is permitted

    • No if an SSL connection to the master is not permitted

    • Ignored if an SSL connection is permitted but the slave server does not have SSL support enabled

    The values of the other SSL-related fields correspond to the values of the MASTER_SSL_CA, MASTER_SSL_CAPATH, MASTER_SSL_CERT, MASTER_SSL_CIPHER, and MASTER_SSL_KEY options to the CHANGE MASTER TO statement. See Section, “CHANGE MASTER TO Syntax”.

  • Seconds_Behind_Master

    This field is an indication of how late the slave is:

    • When the slave is actively processing updates, this field shows the difference between the current timestamp on the slave and the original timestamp logged on the master for the event currently being processed on the slave.

    • When no event is currently being processed on the slave, this value is 0.

    In essence, this field measures the time difference in seconds between the slave SQL thread and the slave I/O thread. If the network connection between master and slave is fast, the slave I/O thread is very close to the master, so this field is a good approximation of how late the slave SQL thread is compared to the master. If the network is slow, this is not a good approximation; the slave SQL thread may quite often be caught up with the slow-reading slave I/O thread, so Seconds_Behind_Master often shows a value of 0, even if the I/O thread is late compared to the master. In other words, this column is useful only for fast networks.

    This time difference computation works even if the master and slave do not have identical clock times, provided that the difference, computed when the slave I/O thread starts, remains constant from then on. Any changes—including NTP updates—can lead to clock skews that can make calculation of Seconds_Behind_Master less reliable.

    This field is NULL (undefined or unknown) if the slave SQL thread is not running, or if the slave I/O thread is not running or is not connected to the master. For example, if the slave I/O thread is running but is not connected to the master and is sleeping for the number of seconds given by the CHANGE MASTER TO statement or --master-connect-retry option (default 60) before reconnecting, the value is NULL. This is because the slave cannot know what the master is doing, and so cannot say reliably how late it is.

    The value of Seconds_Behind_Master is based on the timestamps stored in events, which are preserved through replication. This means that if a master M1 is itself a slave of M0, any event from M1's binary log that originates from M0's binary log has M0's timestamp for that event. This enables MySQL to replicate TIMESTAMP successfully. However, the problem for Seconds_Behind_Master is that if M1 also receives direct updates from clients, the Seconds_Behind_Master value randomly fluctuates because sometimes the last event from M1 originates from M0 and sometimes is the result of a direct update on M1.

Download this Manual
User Comments
  Posted by Alexey Zilber on August 16, 2011
Here's a quick php code snippet to read your master.info and relay-log.info and generate a change master sql command from it. Very useful if you get corrupted relay logs or have had to purge your relay logs, etc.

$mi=fopen('/tmp/master.info','r'); //<-- replace
$ri=fopen('/tmp/relay-log.info','r'); //<-- replace



"CHANGE MASTER TO MASTER_HOST='$master_info[3]',


Sign Up Login You must be logged in to post a comment.