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• tmpdir 

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The path of the directory to use for creating temporary files. It might be useful if your default /tmp directory resides on a partition that is too small to hold temporary tables. This variable can be set to a list of several paths that are used in round-robin fashion. Paths should be separated by colon characters ( : ) on Unix and semicolon characters ( ; ) on Windows. 

tmpdir  can be a non-permanent location, such as a directory on a memory-based file system or a directory that is cleared when the server host restarts. If the MySQL server is acting as a replica, and you are using a non-permanent location for tmpdir , consider setting a different temporary directory for the replica using the slave_load_tmpdir  variable. For a replica, the temporary files used to replicate LOAD DATA  statements are stored in this directory, so with a permanent location they can survive machine restarts, although replication can now continue after a restart if the temporary files have been removed. 

For more information about the storage location of temporary files, see Section B.3.3.5, “Where MySQL Stores Temporary Files” . 

• transaction_alloc_block_size 

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The amount in bytes by which to increase a per-transaction memory pool which needs memory. See the description of transaction_prealloc_size . 

• transaction_isolation 

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