Using pt-table-sync with these options
will report the SQL changes to execute on the Slave to make the Slave match the Master.
The Master is simply connected for comparison purposes.
The Percona Documenation on --print option says
Print queries that will resolve differences.
If you don’t trust pt-table-sync, or just want to see what it will do, this is a good way to be safe. These queries are valid SQL and you can run them yourself if you want to sync the tables manually.
For emphasis : Do not execute the output of
--sync-to-master on a Master. Execute it on a Slave only.
If you are using Circular Replication, do this
echo "SET SQL_LOG_BIN = 0;" > ChangesToSlave.sql
pt-table-sync --print --sync-to-master ... >> ChangesToSlave.sql
then you can run
ChangesToSlave.sql on a Slave.