Server Command Options you can tell whether or not  mlockall()  (and thus this option) is supported by checking to see whether or not it is defined in the system  mman.h  file, like this: If  mlockall()  is supported, you should see in the output of the previous command something like the following: Use of this option may require you to run the server as  root , which, for reasons of security, is normally not a good idea. See Section 6.1.5, “How to Run MySQL as a Normal User” . On Linux and perhaps other systems, you can avoid the need to run the server as root  by changing the  limits.conf  file. See the notes regarding the memlock limit in Section 8.12.3.2, “Enabling Large Page Support” . You must not use this option on a system that does not support the  mlockall() system call; if you do so,  mysqld  is very likely to exit as soon as you try to start it. The block size to be used for  MyISAM  index pages. Do not read any option files. If program startup fails due to reading unknown options from an option file, --no-defaults  can be used to prevent them from being read. This must be the first option on the command line if it is used. For additional information about this and other option-file options, see Section 4.2.2.3, “Command-Line Options that Affect Option-File Handling” . This option is deprecated as of MySQL 8.0.16. It is superseded by the  -- upgrade  option, which provides finer control over data dictionary and server upgrade behavior. 746 Command-Line Format --no-dd-upgrade[={OFF|ON}] Deprecated 8.0.16 Type Boolean Default Value OFF Note • --no-defaults • --no-dd-upgrade • --myisam-block-size= N shell>  grep mlockall /usr/include/sys/mman.h extern int mlockall (int __flags) __THROW; Important Command-Line Format --myisam-block-size=# Type Integer Default Value 1024 Minimum Value 1024 Maximum Value 16384