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Pauses purging of delete-marked records while allowing the purge view to be updated. This option artificially creates a situation in which the purge view is updated but purges have not yet been performed. This option is only available if debugging support is compiled in using the WITH_DEBUG CMake  option. 

• innodb_trx_rseg_n_slots_debug 

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Sets a debug flag that limits TRX_RSEG_N_SLOTS  to a given value for the trx_rsegf_undo_find_free  function that looks for free slots for undo log segments. This option is only available if debugging support is compiled in using the WITH_DEBUG CMake  option. 

• innodb_undo_directory 

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The path where InnoDB  creates undo tablespaces. Typically used to place undo tablespaces on a different storage device. 

There is no default value (it is NULL). If the innodb_undo_directory  variable is undefined, undo tablespaces are created in the data directory. 

The default undo tablespaces ( innodb_undo_001  and innodb_undo_002 ) created when the MySQL instance is initialized always reside in the directory defined by the innodb_undo_directory  variable. 

Undo tablespaces created using CREATE UNDO TABLESPACE  syntax are created in the directory defined by the innodb_undo_directory  variable if a different path is not specified. 

For more information, see Section 15.6.3.4, “Undo Tablespaces” . 

