If you want to share a database with a couple of other users, putting the datadir in OneDrive isn't going to work.

MySQL stores data in the files under the datadir, that's true. They're stored in files called tablespaces which have the .ibd extension.

But as you do INSERT/UPDATE/DELETE operations, data is temporarily stored in memory and in the transaction logs (ib_logfile*. MySQL has to do a delicate coordination between these, to save data in a durable way, while ensuring good performance. It works well, but only if the MySQL Server is the only process writing to the files.

OneDrive is not coordinating with MySQL at all. It will periodically check for files that have changed since it last did a sync. The interval OneDrive checks files is about every 10 minutes, and this is not configurable.

OneDrive may choose to sync the files at a moment after you've done some INSERT/UPDATE/DELETE operations, and the data is modified in RAM, but hasn't yet been updated in the tablespace files on disk.

Once you've committed a change, it must also be safely stored in the transaction log, even if it isn't updated in the tablespace. But if your friends receive the files in this state (transaction log contains changes which aren't present in the tablespace), they can reconstruct the data from your RAM that they didn't get. This is called InnoDB crash recovery. MySQL Server does if automatically if it starts up and finds the transaction log contains changes that aren't in the tablespace. It assumes you had a sudden reboot and lost what was in RAM.

If your friends try to just keep their MySQL Server running continuously, reading a datadir that is simultaneously being updated by their one OneDrive, it'll basically overwrite their files and MySQL will become confused. It only checks to see if it should do crash recovery as MySQL Server starts. So if the files change in unexpected ways while MySQL Server is already running, it'll just conclude that your hard drive has gotten corrupted. It'll probably report a fatal error and shut down MySQL.

Also if your friends try to make changes of their own to the database, their changes would conflict with the updates from OneDrive. Then their attempts to overwrite files would eventually be synchronized in the opposite direction via OneDrive, and would eventually corrupt your database too. This would happen without warning at 10 minute intervals, whenever OneDrive chose to do its file sync.

So I'm afraid OneDrive is not the solution to share your database.

Alternatives that do have a chance of working include:

• Hosting a single instance of MySQL Server on a website that you all share, and giving each of you a client that can use the database. A popular free client is phpMyAdmin. That way there'd be only one instance of MySQL Server, one datadir, even though you each would be concurrent clients reading and writing data. This is the simplest solution, most likely to work.

• Exporting the data from your MySQL Server instance using mysqldump periodically, and putting the export file on OneDrive, or sending it to your friends through email or any other means. Then they would have to import that data to their MySQL Server manually. This would overwrite any changes they had done to their database, but it wouldn't appear as corruption. If they want to send changes back to you, they could do a similar operation: export their database, put the dump file on OneDrive, then you'd get their dump file and import it to your MySQL Server instance, overwriting any changes you had done locally since the last time you sent your export to your friends.

• Use a MySQL add-on for multi-server synchronous replication, such as InnoDB Group Replication or Percona XtraDB Cluster. But this is probably too complex for you to set up if you're a newbie with MySQL.