MySQL 8.0 FAQ: Replication Note A.14 MySQL 8.0 FAQ: Replication This example uses https://ninja-build.org/ as a build system instead of make. In the following section, we provide answers to questions that are most frequently asked about MySQL Replication. Yes, networking must be enabled on the source and replica. If networking is not enabled, the replica cannot connect to the source and transfer the binary log. Verify that the  skip_networking  system variable has not been enabled in the configuration file for either server. Check the  Seconds_Behind_Master  column in the output from  SHOW REPLICA | SLAVE STATUS . See Section 17.1.7.1, “Checking Replication Status” . No, it does not. The replica can go down or stay disconnected for hours or even days, and then reconnect and catch up on updates. For example, you can set up a source/replica relationship over a dial-up link where the link is up only sporadically and for short periods of time. The implication of this is that, at any given time, the replica is not guaranteed to be in synchrony with the source unless you take some special measures. To ensure that catchup can occur for a replica that has been disconnected, you must not remove binary log files from the source that contain information that has not yet been replicated to the replicas. Asynchronous replication can work only if the replica is able to continue reading the binary log from the point where it last read events. 5270 A.14.1 Must the replica be connected to the source all the time? .................................................... 5270 A.14.2 Must I enable networking on my source and replica to enable replication? ............................. 5270 A.14.3 How do I know how late a replica is compared to the source? In other words, how do I know the date of the last statement replicated by the replica? ....................................................... 5270 A.14.4 How do I force the source to block updates until the replica catches up? ............................... 5271 A.14.5 What issues should I be aware of when setting up two-way replication? ................................ 5271 A.14.6 How can I use replication to improve performance of my system? ........................................ 5271 A.14.7 What should I do to prepare client code in my own applications to use performance-enhancing replication? ......................................................................................................................... 5272 A.14.8 When and how much can MySQL replication improve the performance of my system? ........... 5272 A.14.9 How can I use replication to provide redundancy or high availability? .................................... 5273 A.14.10 How do I tell whether a replication source server is using statement-based or row-based binary logging format? ........................................................................................................ 5273 A.14.11 How do I tell a replica to use row-based replication? ......................................................... 5273 A.14.12 How do I prevent  GRANT  and  REVOKE  statements from replicating to replica machines? ....... 5273 A.14.13 Does replication work on mixed operating systems (for example, the source runs on Linux while replicas run on macOS and Windows)? ...................................................................... 5273 A.14.14 Does replication work on mixed hardware architectures (for example, the source runs on a 64-bit machine while replicas run on 32-bit machines)? ........................................................ 5273 A.14.1. Must the replica be connected to the source all the time? A.14.2. Must I enable networking on my source and replica to enable replication? A.14.3. How do I know how late a replica is compared to the source? In other words, how do I know the date of the last statement replicated by the replica?