Resources needed for operation

In order to operate, SHC-OSD needs a fixed batch task which is automatically started by SHC-OSD when the subsystem is started. It is started with the standard job class (for batch under TSOS) and without any time limit. The task has the job name SHCUSERT. SHC-OSD dynamically generates further tasks in order to execute commands.

To support SHC-OSD operation, at least 512 MB of additional capacity must be defined in the paging area. If a number of SHC-OSD commands are run in parallel, the memory requirements may be double this size.

The ADDRESS-SPACE-LIMIT must be at least 512 MB for the user IDs TSOS and SYSROOT.

The SHC-OSD commands are executed in fork tasks of the SHCUSERT batch task. Fork tasks do not inherit the CPU-LIMIT=*NO setting of the batch tasks they generate. The standard job class setting of the TSOS ID is valid for the fork tasks. (For information on fork tasks, refer to the “C Library Functions” manual [4].)

The POSIX file system must be configured for the use of SHC-OSD.
40-200 MB of free disk space for logging files in the /shcosd und /symapi subdirectories must be available in the /var file system. Disk space requirements are largely dependent
on the number and size of logging files stored. The system administrator should delete or archive logging files regularly.
The SHC-OSD parameter file contains a setting for the automatic deletion of the logging file of SHC-OSD (see "Configuration of SHC-OSD").

SHC-OSD uses POSIX semaphores (variables which control access to a shared resource). At least 20 free semaphore records should be available for operation (see "POSIX" manuals [2] and [3]).
SHC-OSD uses up to two POSIX shared memory segments.

You are recommended not to use the POSIX functionality "Journaling for File Systems" when all the following conditions are fulfilled for the pubset on which POSIX is installed:

• The pubset consists of multiple volumes

• The volumes are configured for DRV

• The pubset is mirrored locally or remotely

• The mirrors for the pubset are to be split consistently with SHC-OSD commands using

  HOLD-IO=*UNTIL-...

When "Journaling for File Systems" is used in POSIX, this can result in competing I/O activities which impede consistent splitting of the mirrors.

Using PTHREADS

SHC-OSD requires the PTHREADS functionality in BS2000 and StorMan.
PTHREADS is a component part of BS2000.

The SYSPAR.SHC-OSD.<ver>.PTH file supplied with SHC-OSD contains the options for controlling PTHREADS operation of SHC-OSD.

SHC-OSD evaluates the corresponding parameter files for PTHREADS at startup time. The files can be edited. However, the values of the files supplied should only be modified in exceptional cases. Modifications become effective only after SHC-OSD has been restarted.  

The SYSPAR.SHC-OSD.<ver>.PTH file contains the following options:

MINTH=	Defines the minimum number of thread tasks. The number of thread tasks should always be less than or equal to the number of processors. The following specifications are possible:
	*STD	Stands for 1 (should not be changed)
	n	Integer between 1 and 59
MAXTH=	Defines the maximum number of thread tasks. The option can increase the space requirements for the tasks. The size of the memory pool may therefore also need to be adjusted (using the SHAMS option). The number of thread tasks should always be less than or equal to the number of processors. The following specifications are possible:
	*STD	Stands for 1 (should not be changed)
	n	Integer between 1 and 59
SHAMS=	Defines the number of pages for the memory pool. This contains the application code and various runtime systems or parts thereof. The size of the memory pool required also depends on the number of tasks defined with MAXTH and the possible number of threads. If MAXTH is much larger than the default value or if the application works with a very large number of parallel threads, the memory pool must also be enlarged. The following specifications are possible:
	*STD	Stands for 32768 (PTHREADS default value). The value 131072 is recommended for SHC-OSD (setting when supplied).
	n	Integer between 1 and 2147483647
BUSYC=	Defines the number of busy loops of PTHREADS before the next processor is released for the next request. This setting has repercussions on the CPU utilization of the batch task SHCUSERT, in particular in monoprocessor mode. The following specifications are possible:
	n	Integer between 1 and 100000 The value 10 is recommended for SHC-OSD (default value).

Example

The SYSPAR.SHC-OSD.<ver>.PTH file supplied contains the following settings which should generally not be changed:

MINTH=1,
MAXTH=1,
SHAMS=131072
BUSYC=10

The SYSPAR.SHC-OSD.<ver>.PTH file corresponds to the global PTHREADS options file. It only contains the parameters which are relevant for SHC-OSD. It should only be modified in exceptional cases.