The performance-related file attributes PERFORMANCE, USAGE and DISK-WRITE were introduced in conjunction with the hiperfile concept:
PERFORMANCE Specifies the desired performance of I/O behavior for file access
USAGE Indicates whether the performance is requested for read access only, for write access only or for both types of access
DISK-WRITE Determines at which point during high-performance file processing data consistency for write operations is required.
From BS2000 OS DX, effective BS2000 V21.0A onwards, (USER-)PFA is no longer supported.
Performance-related file attributs with SF pubsets
On former BS2000 versions the performance-related file attributes controled for SF pubserts the usage of caches only. Since from BS2000 V21.0A on PFA isn't supported anymore and therefore no cache is assigned to the SF pubsets, the attributes PERFORMANCE, USAGE and DISK-WRITE are irrelevant. The performance behavior is exclusively determined by the location of the file.
The user requires very detailed knowledge of the characteristics of the various media to be able to obtain the desired performance behavior.
Performance-related file attributs with SM pubsets
With SM pubsets, the performance-related file attributes are used to select the volume set that is best suitable as location of a particular file: When a new file is created, its performance attributes are used automatically to determine the volume set whose performance profile is best suited to meet the file requirements.
The performance profile of a volume set can be displayed by means of the SHOW-PUBSET-DEFINITION-FILE command. It is derived from the performance range of a volume set and the constraints on secure writing as a result of higher performance values.
The SHOW-PUBSET-DEFINITION-FILE command supplies a list of performance values for volume sets. Note, however, that with nonsecure (volatile) caches, higher performance can only be offered for file processing that does not require data consistency after each write operation. This constraint with respect to higher performance is taken into account by the performance-relevant attribute WRITE-CONSISTENCY:
WRITE-CONSISTENCY=*BY-CLOSE indicates that higher performance can be offered only at the expense of secure writing.