Replication and Binary Logging Options and Variables Disable or enable automatic purging of relay logs as soon as they are no longer needed. The default value is 1 (enabled). This is a global variable that can be changed dynamically with  SET GLOBAL relay_log_purge =  N . Disabling purging of relay logs when enabling the  --relay-log-recovery option risks data consistency and is therefore not crash-safe. Default Value ON • --relay-log-space-limit= size Command-Line Format --relay-log-space-limit=# System Variable relay_log_space_limit Scope Global Dynamic No SET_VAR  Hint Applies No Type Integer Default Value 0 Minimum Value 0 Maximum Value 4294967295 This option places an upper limit on the total size in bytes of all relay logs on the replica. A value of 0 means “no limit” . This is useful for a replica server host that has limited disk space. When the limit is reached, the I/O thread stops reading binary log events from the source server until the SQL thread has caught up and deleted some unused relay logs. Note that this limit is not absolute: There are cases where the SQL thread needs more events before it can delete relay logs. In that case, the I/O thread exceeds the limit until it becomes possible for the SQL thread to delete some relay logs because not doing so would cause a deadlock. You should not set  --relay-log-space-limit  to less than twice the value of  --max-relay-log-size  (or  --max-binlog-size  if  --max-relay-log-size  is 0). In that case, there is a chance that the I/O thread waits for free space because  --relay-log-space- limit  is exceeded, but the SQL thread has no relay log to purge and is unable to satisfy the I/O thread. This forces the I/O thread to ignore  --relay-log-space-limit  temporarily. • --replicate-do-db= db_name Command-Line Format --replicate-do-db=name Type String Creates a replication filter using the name of a database. Such filters can also be created using  CHANGE REPLICATION FILTER REPLICATE_DO_DB . This option supports channel specific replication filters, enabling multi-source replicas to use specific filters for different sources. To configure a channel specific replication filter on a channel named channel_1  use  --replicate-do-db: channel_1 : db_name . In this case, the first colon is interpreted as a separator and subsequent colons are literal colons. See Section 17.2.5.4, “Replication Channel Based Filters”  for more information. Global replication filters cannot be used on a MySQL server instance that is configured for Group Replication, because filtering transactions on some servers would make the group unable to reach agreement on a consistent state. Channel specific replication filters can be used on replication channels that are not Note 3507