Solaris 8 introduced a new mechanism to change the number of ptys allowed in
the 
system.
Unlike previous releases of Solaris, the total number of ptys configurable in 
the systme
depend on the total kernel memory available.

Three related variables in /etc/system file are used in the configuration 
process:

 pt_cnt - Default maximum number of ptys

 pt_pctofmem - Percentage of kernel memory that can be dedicated
               to pty support structures

 pt_max_pty  - Hard maximum for number of ptys

1) pt_cnt is the minimum number of ptys in the system
   with default value of zero, which tells the system to
   limit logins based on the amount of memory specified in
   pct_pctofmem, unless pt_max_pty is set.

2) If pt_cnt is non-zero, ptys are allocated until pt_pctofmem limit.
   When threashold is reached, the system looks at pt_max_pty.
   If that has a non-zero value, it is compared to pt_cnt.
   - And if pt_cnt is less than pt_max_pty, the pty allocation is allowed.
   If pt_max_pty is zero, pt_cnt is compared to the number of ptys
   supported based on pt_pctofmem.
   - And if pt_cnt is less than this value, the pty allocation is allowed.

If you want to put a hard limit on ptys that is different than
the maximum derived from pt_pctofmem,
you should set pt_cnt and ptms_ptymax in /etc/system to the number
of ptys desired.
The setting of ptms_pctofmem is not relevant in this case.

If you want to dedicate a different percentage(default is 5%) of
system memory to pty support and let the operating system manage
the explicit limits,
you should do the following: 
   o Do not set pt_cnt or ptms_ptymax in /etc/system
   o Set pt_pctofmem in /etc/system to the desired percentage.
     For example, set for a 10% setting.
     "pt_pctofmem=10"