What is MySQL slave lag?

What is MySQL slave lag?

MySQL Curriculum Developer. Replication lag occurs when the slaves (or secondaries) cannot keep up with the updates occuring on the master (or primary). Unapplied changes accumulate in the slaves’ relay logs and the version of the database on the slaves becomes increasingly different from that of the master.

How can I tell if MySQL is master or slave?

Check MySQL Replication Status on Query Servers

1. Start the MySQL command-line utility on the slave server: # cd /opt/mysql/mysql/bin.
2. Check the replication status using the show slave status command (the status of the slave server is conveyed by the Slave_IO_Running and Slave_SQL_Running column values):

Is there a problem with MySQL replication slave lag?

Here on the Percona MySQL Supportteam, we often see issues where a customer is complaining about replication delays – and many times the problem ends up being tied to MySQL replication slave lag.

Why is my Slave lagging behind the Master?

I have a master/slave replication on my MySql DB. my slave DB was down for a few hours and is back up again (master was up all the time), when issuing show slave status I can see that the slave is X seconds behind the master. the problem is that the slave dont seem to catch up with the master, the X seconds behind master dont seem to drop…

Can a slave delete a table without a PK?

If you execute e.g. one delete statement on the master to delete 1 million records on a table without a PK or unique key then only one full table scan will take place on the master’s side, which is not the case on the slave.

What does seconds behind mean in MySQL replication?

“seconds behind” isn’t a very good tool to find out how much behind the master you really is. What it says is “the query I just executed was executed X seconds ago on the master”. That doesn’t mean that you will catch up and be right behind the master the next second.