z/OS UNIX provides
the system programmer with a number of controls that monitor and
tune the use of system resources by users. As part of the tuning
process, you can follow these initial rules of thumb:
- Assume that each user will consume up to double the system resources
required for a TSO/E user.
- Assume that at most 4 PTYs will be required per average user.
- Assume that the starting point for maximum processes per user
is 25.
- Assume that 4 concurrent processes will be required by the average
active user.
- Assume that 5 processes will be required for various daemons.
- Assume that 3 concurrent address spaces will be required by the
average active user. This number will be high if your users are running
with the _BPX_SHAREAS environment variable set to YES.
- Assume that no user, including servers or daemons,
needs more than 2048 files open at one time for Unicode Services conversion.
In this case, the default MAXIOBFUSER setting of 2048 (which equals
2 G of above the bar storage) is enough and no changes to the initial
setting is necessary.
Tip: If you have a few users who need a large number of
processes, use the PROCUSERMAX keyword in the OMVS segment to set
the process limit for these users.
For example, assume that your system supports 600 TSO/E users and
has enough capacity for 20 additional users. Rather than adding more
TSO/E work, you want to allow TSO/E users to access
z/OS UNIX. You have
no other
z/OS UNIX work
on your system at this time. In this example the initial settings
in BPXPRMxx might be:
MAXUIDS(20)
MAXPTYS(80)
MAXPROCUSER(25)
MAXPROCSYS(85)
Table 1 shows
how the initial settings were calculated.
Table 1. Calculating
initial settings when tuning process activity. This table
lists the initial settings for certain BPXPRMxx parameters.Parameter |
Initial setting |
Note |
---|
MAXUIDS |
20 |
If you allow 20 current TSO/E users to access
the z/OS UNIX system,
each of them could consume twice the resource they normally used for
TSO/E. This would require all your remaining system resources. |
MAXPTYS |
80 |
Assume that 4 PTYs are needed per user. Users
can login with multiple sessions at the same time |
MAXPROCUSER |
25 |
This should normally be a reasonable starting
point. Some users might require more processes, depending on the work
they are doing. This value can be set only on a system-wide basis. |
MAXPROCSYS |
85 |
Assume that you need 4 processes per user and
5 processes for daemons. (20 users * 4) + 5 daemons = 85 processes. |