InnoDB System Variables 3241 When enabled,  InnoDB  writes NULLs to newly allocated pages. When disabled, space is allocated using posix_fallocate()  calls, which reserve space without physically writing NULLs. For more information, see Section 15.6.3.8, “Optimizing Tablespace Space Allocation on Linux” . The  InnoDB  shutdown mode. If the value is 0,  InnoDB  does a slow shutdown, a full purge and a change buffer merge before shutting down. If the value is 1 (the default),  InnoDB  skips these operations at shutdown, a process known as a fast shutdown. If the value is 2,  InnoDB  flushes its logs and shuts down cold, as if MySQL had crashed; no committed transactions are lost, but the crash recovery operation makes the next startup take longer. The slow shutdown can take minutes, or even hours in extreme cases where substantial amounts of data are still buffered. Use the slow shutdown technique before upgrading or downgrading between MySQL major releases, so that all data files are fully prepared in case the upgrade process updates the file format. Use  innodb_fast_shutdown=2  in emergency or troubleshooting situations, to get the absolute fastest shutdown if data is at risk of corruption. By default, setting  innodb_fil_make_page_dirty_debug  to the ID of a tablespace immediately dirties the first page of the tablespace. If  innodb_saved_page_number_debug  is set to a non- default value, setting  innodb_fil_make_page_dirty_debug  dirties the specified page. The Command-Line Format --innodb-fil-make-page-dirty-debug=# System Variable innodb_fil_make_page_dirty_debug Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer Default Value 0 Maximum Value 2**32-1 • innodb_fil_make_page_dirty_debug • innodb_fast_shutdown Command-Line Format --innodb-fast-shutdown=# System Variable innodb_fast_shutdown Scope Global Dynamic Yes SET_VAR  Hint Applies No Type Integer Default Value 1 Valid Values 0 1 2