Please ensure you have a working backup of your database
before you perform any of the following steps.
Follow these steps from the official Maria DB documentation to shrink the size of your
Decreasing the Size
In cases where the InnoDB system tablespace has grown too large, the process to reduce it in size is a little more complicated than increasing the size. MariaDB does not allow you to remove data from the tablespace file itself. Instead you need to delete the tablespace files themselves, then restore the database from backups.
The backup utility mysqldump produces backup files containing the SQL statements needed to recreate the database. As a result, it restores a database with the bare minimum data rather than any additional information that might have built up in the tablespace file.
Use mysqldump to backup all of your InnoDB database tables, including the system tables in the mysql database that use InnoDB. You can find out what they are using the Information Schema.
SELECT TABLE_NAME FROM information_schema.TABLES
WHERE TABLE_SCHEMA = 'mysql' AND ENGINE = 'InnoDB';
If you only use InnoDB, you may find it easier to back up all databases and tables.
$ mysqldump -u root -p --all-databases > full-backup.sql
Then stop the MariaDB Server and remove the InnoDB tablespace files. In the data directory or the InnoDB data home directory, delete all the ibdata and ib_log files as well as any file with an .ibd or .frm extension.
Once this is done, restart the server and import the dump file:
$ mysql -u root -p < full-backup.sql
Reference: InnoDB System Tablespaces (MariaDB Documentation)
Answering Your Questions
Is it OK if delete it ?
No, unless you have a working backup and have performed the above steps to save relevant data.
Will be recreated when I restart maria db?
Yes, but what use is an empty non-functional