MySQL 5.7 Reference Manual Including MySQL NDB Cluster 7.5 and NDB Cluster 7.6

16.2.2.4 Replication Channel Naming Conventions

This section describes how naming conventions are impacted by replication channels.

Each replication channel has a unique name which is a string with a maximum length of 64 characters and is case-insensitive. Because channel names are used in replication metadata repositories, the character set used for these is always UTF-8. Although you are generally free to use any name for channels, the following names are reserved:

The name you choose for a replication channel also influences the file names used by a multi-source replica. The relay log files and index files for each channel are named relay_log_basename-channel.xxxxxx, where relay_log_basename is a base name specified using the relay_log system variable, and channel is the name of the channel logged to this file. If you do not specify the relay_log system variable, a default file name is used that also includes the name of the channel.