Server System Variables Scope Global, Session Dynamic Yes SET_VAR  Hint Applies No Type Boolean Default Value OFF When this variable is enabled, the server does not use the optimized method of processing an  ALTER TABLE  operation. It reverts to using a temporary table, copying over the data, and then renaming the temporary table to the original, as used by MySQL 5.0 and earlier. For more information on the operation of  ALTER TABLE , see Section 13.1.9, “ALTER TABLE Statement” . ALTER TABLE ... DROP PARTITION  with  old_alter_table=ON  rebuilds the partitioned table and attempts to move data from the dropped partition to another partition with a compatible  PARTITION ... VALUES  definition. Data that cannot be moved to another partition is deleted. In earlier releases,  ALTER TABLE ... DROP PARTITION  with  old_alter_table=ON  deletes data stored in the partition and drops the partition. The number of file descriptors available to  mysqld  from the operating system: The effective  open_files_limit  value is based on the value specified at system startup (if any) and the values of  max_connections  and  table_open_cache , using these formulas: • open_files_limit •At startup,  mysqld  reserves descriptors with  setrlimit() , using the value requested at by setting this variable directly or by using the  --open-files-limit  option to  mysqld_safe . If mysqld  produces the error  Too many open files , try increasing the  open_files_limit  value. Internally, the maximum value for this variable is the maximum unsigned integer value, but the actual maximum is platform dependent. •At runtime, the value of  open_files_limit  indicates the number of file descriptors actually permitted to  mysqld  by the operating system, which might differ from the value requested at startup. If the number of file descriptors requested during startup cannot be allocated,  mysqld  writes a warning to the error log. • 10 + max_connections + (table_open_cache * 2) • max_connections * 5 •MySQL 8.0.19 and higher: The operating system limit. 847 Command-Line Format --open-files-limit=# System Variable open_files_limit Scope Global Dynamic No SET_VAR  Hint Applies No Type Integer Default Value 5000, with possible adjustment Minimum Value 0 Maximum Value platform dependent