Placement of critical data
The disk or disks that contain the system reserved pages, the physical log, and the dbspaces that contain the logical-log files are critical to the operation of the database server. The database server cannot operate if any of these elements becomes unavailable. By default, the database server places all three critical elements in the root dbspace.
To arrive at an appropriate placement strategy for critical data, you must make a trade-off between the availability of data and maximum logging performance.
The database server also places temporary table and sort files in the root dbspace by default. You should use the DBSPACETEMP configuration parameter and the DBSPACETEMP environment variable to assign these tables and files to other dbspaces. For details, see Configure dbspaces for temporary tables and sort files.