In differential or incremental restores, the MySQL plugin will restore the binary logs to a temporary directory to be applied into the database.
This temporary location is always NETVAULT_HOME/tmp/mysql, regardless of the NetVault client's setting for NetVault temporary directory.
The MySQL plugin has a hard coded dependency that the NetVault temp directory is named "tmp" and always located in the NetVault home directory.
A workaround is to place a symbolic link called mysql in the NETVAULT_HOME/tmp, refer this symbolic link to a volume with required space.
This is an issue with MySQL plugin versions 4.0.5 and earlier. Later releases of the plugin acknowledge the NetVault's temporary directory setting and locates the mysql directory there.