UNIX Disk Configuration

Filestore and partition databases in a UNIX system require different disk configurations to implement a Shadow Database pair. For:

Partition Database Four, or more, database partitions, two mirrored clean log partitions and two mirrored raw log partitions are required.

Filestore Databases Two database partitions, two mirrored clean log partitions and two mirrored raw log partitions are required.

Partition Databases

For Partition Databases the top directory structure for each database must be enabled on its own partition separate from the bulk of the database. Hence a pair of Shadow Partition Databases requires at least four partitions, one for each top database directory (live and Shadow) and one or more for the main database structure of each database. The clean log partition must be on a resilient disk sub-system, for example, mirrored disks or RAID disks.

The top database directory requires only a small partition as long as the temporary files directory tmp is moved from it. The top database directory normally requires a large amount of disk space to allow for temporary files created in tmp when doing large sorts. However, you can relocate the tmp directory by defining the configuration parameter TempDir in the database configuration file. For example, the entry:

TempDir=/user0/tmp

moves the tmp directory to the /user0 partition. The disk space required by the database directory is then small.

The tmp directory is normally cleared by the database daemon at boot time. This can be prevented by setting the ClearTempDir parameter in the database configuration file to any value other than Y. For example, the entry:

ClearTempDir=N

prevents tmp being cleared each time the database daemon is started.

The database directory partition and virtual partition for each half of the Shadow pair (live and Shadow) can be on the same set of disks. However, it is recommended that partitions for the live and Shadow Databases must be located on different sets of disks.

Filestore Databases

Each File Store Database in a Shadow pair must be located on its own disk partition on separate sets of disks. No other data must exist on either the live or Shadow partition. More than one Shadow pair can reside on the same system provided that each database resides on a different partition. The clean log partition must be on mirrored disks to provide for resilience in the event of a disk crash.

Clean logs

The clean log directories for both the live and Shadow Databases must be located in the same disk partition. So, for example, if the clean log partition is mounted at /cleanlog, for the Shadow pair dbase1 and dbase2 you will create the clean log directories /cleanlog/dbase1 and /cleanlog/dbase2. This can be carried out using option 1 on the Configuration and Setup  menu, see Defining/Redefining a Shadow Database.