Task management

In BS2000, logically interrelated requests to the system and their execution are managed in the form of tasks.

If these requests to the system are UTM applications, the various transaction codes within UTM can be controlled by means of so-called TAC classes. Similar resources are available here as are used for tasks and categories under PRIOR or PCS.
An introductory summary on this subject is provided on "Optimizing the various phases".
Detailed information can be found in the openUTM manuals.

Basic principles of task management

Both user tasks and system tasks are monitored and controlled by the task management routines.

For a task to be able to run, task management must make the following decisions:

• allocation of authorization to use main memory --> activation

• allocation of the resource CPU --> initiation

Initiation is possible for already activated tasks only.

Criteria for managing main memory:

• multiprogramming level (MPL) per category

• Priority

• resource workload (CPU, main memory, paging activity)

• system services rendered (CPU time, number of I/O operations).

Criterion for managing the resource CPU is only the priority.

If multiprocessors are in use and the TANGRAM function has been activated, the assignment algorithm can result in a different initiation sequence (see also section“TANGRAM concept”).

Internal category name

Both task categories and priorities are given a system-internal representation which differs from that at the user interface.

The default categories have fixed identifiers:

Category	Category identifier
SYS	0
DIALOG	1
BATCH	2
TP	3
xy	4
. . .	. . .

Internal priority

The specified variable priorities are weighted according to the importance of the category concerned (represented by the WEIGHT-CODE parameter). The variable internal priority is a function of:

• the external priority

• the WEIGHT-CODE (W) of the category to which the task belongs

• the sum S of the weights of all categories

S = W_SYS + W_TP + W_DIAL + W_BATCH + W_xy + ...

Variable internal priority = 1 + (256 - external priority) * 0,5 * (1 + W / S)

Fixed external priorities assigned by the user are converted as follows:

Fixed internal priority = 256 - external priority

The internal priority serves as a basis for calculating the activation and initiation priorities.