Can anybody please mention the internals that works when we use mysqldump
as follows:


*mysqldump --single-transaction --all-databases > backup_sunday_1_PM.sql*

MySQL manual says:

This backup operation acquires a global read lock on all tables at the
beginning of the dump (using *FLUSH TABLES WITH READ LOCK
<http://dev.mysql.com/doc/refman/5.6/en/flush.html>*). As soon as this lock
has been acquired, the binary log coordinates are read and the lock is
released. If long updating statements are running when the FLUSH
<http://dev.mysql.com/doc/refman/5.6/en/flush.html> statement is issued,
the backup operation may stall until those statements finish. After that,
the dump becomes lock-free and does not disturb reads and writes on the
tables.

Can anyone explain it more? Please.



Best Regards,
Geetanjali Mehra
Senior Oracle and MySQL DBA Corporate Consultant and Database Security
Specialist