Creating system files

System files are required by the operating system to complete its tasks. Because of their crucial importance, these files are amongst those that have the greatest effect on the performance of an IT system. Of the many system files, the following are the ones accessed most regularly:

Function	DMS name
File catalog (SF pubset) File catalog (SM pubset)	$TSOS.TSOSCAT $TSOS.TSOSCAT.<volset-id>
Paging areas	$TSOS.SYS.PAGING.<vsn>
Background storage for access method EAM	$TSOS.SYSEAM

Priority must be given to avoiding access conflicts when creating these files.

The usual way of reducing the probability of access conflicts is to distribute the files over several volumes. If, for reasons of economy (e.g. utilization of disk capacity), user files and system files are placed on the same volume, then it is desirable to select user files which are not frequently used.

The characteristic features of system files are the file size and the access frequency.

If a system has already been set up, the location of the paging areas can only be changed with great difficulty. Therefore particular attention must be paid to the location and size of this system file at configuration.

If the system is being used for program development, then cataloged module libraries (TASKLIBs) and macro libraries are often accessed so regularly that their location must be taken into consideration at configuration.