What is Magento migration tool and how to use it?

Having developed a Magento 1 to Magento 2 migration plan, you need to transfer data. Magento Data Migration Tool is a good supplement for this task, the tool:

• checks for the converges between Magento’s database structures;
• monitors progress in data transferring;
• logs the process and,
• runs confirmation tests.

You can read more about the tool in the official devdocs.

What do you need to know before using Magento migration tool?

• Before migrating, make sure you’ve stopped all Magento cron jobs;
• During migration, do not implement any changes into Magento admin, except for order management;
• During migration, do not modify any code;
• During migration, do not perform any changes in the Magento frontend.

How to launch data transferring with Magento migration tool?

• Log into your Magento server as a user who can write to the Magento file system.
• Add <magento_root>/bin to your system PATH to run commands from any directory. Example of bash shell for CentOS: $ export PATH=$PATH:/var/www/html/magento2/bin
• Now, we'll consider the example of a typical migration command: $ bin/magento migrate:<mode> [-r|--reset] {<path to config.xml>}

In the above command:
<mode> can be settings, data, delta;
[-r|--reset] means an argument that starts migration;
{<path to config.xml>} is an absolute file system path to config.xml.

See more clarifications here.

Remember that when creating the data transferring tool, Magento implied the next migration order:

• settings;
• data;
• changes.

and you are called for transferring all the data in the same way.