I have several AIX servers running 5.2.

What is the default max size for a group in /etc/group?
How do I change the default max size for a group to be unlimited (if possible)?

Thanks

There is a file called /usr/include/sys/limits.h - which shows system limits (not sets them)

In there, I suspect the one you are interested in is:
/* RUN-TIME INVARIANT VALUES
The system supports the following fixed magnitude limitations.
*/
#define MAX_INPUT 512 /* max bytes in terminal
input queue, >= 256+64 */

#define NGROUPS_MAX 128 /* max number of supplementary group IDs
per process, >= 0 */

now, why it says "per process" seems unusual, what limit did you hit ?

here is the same line:

#define NGROUPS_MAX 128 /* max number of supplementary group IDs per process, >= 0 */

Is the 128, the number of groups a user can belong to? I'm assuming the "group IDs per process" is actually groups per user.

On our server, 16 groups is the maximum for any given user. We were told that we can adjust this number to 32, but where is this setting?

I'm sorry I can't help with the N_GROUPS_MAX question. That parameter is a limit to the number of groups of which a user can be a member. I believe your original question quoted above is about the number of members a group can have which is sort of 90 degrees different.

I also would like to know if there is a limit on the line length of lines in /etc/group. I believe there is and that it is about 1000 characters but search as I have I cannot find any information about it. It may be that there is a limit imposed by ypmake which promulgates the /etc/group file.

Did you find an answer to your original question?

Can anybody advise where else I could look to find the answer?

Thx

IIRC there are problems when the maximum length of a line in /etc/groups exceeds 2048 chars (think limit depends on the tool (NIS,vi,grep ...) one uses for editing this file). To get by this you could define several group names which all have the same group ID with each line length staying below the limit. This will lead to all users belonging to the same group.
group01:400:nancy,shirley,tina,ethel,....
group02:400:anne,doreen,emma,herriette,....
group03:400:amy,dorothea,carly,donna,....