If you're unable to start MySQL after these changes, it means the MySQL does not support the parameters you've entered. The best way to see why this is happening by looking at the mysql logs. You can also post your questions in mysql forums for getting better solution.
I understand you are trying to use MySQL 8.1 with Jira. Unfortunately, Jira Server does not yet support this version of that database. Please see our Supported platforms documentation for Jira 8.4. While MySQL is listed on that page, it does indicate that only the 5.6.x and 5.7.x version are actually supported for current Jira 8.4 installations. Please also note that you do need to use the MySQL Connector/J 5.1 driver. Trying to use other more recent versions are known to cause problems here.
Once you have a supported database version, I would recommend trying to follow our guide on Connecting Jira applications to MySQL 5.7. This way you can make sure that you setup this database in a manner that Jira is expecting to be avoid a number of known configuration problems.
I hope this helps.
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