By Paul Murphy, author of The Unix Guide to Defenestration
Does 2097151 mean anything to you?
It's a Solaris magic number. Specifically it's the highest identifier the regular archive tools (including many third party tools and ar, tar, gtar, cpio) will accept.
Thus a uid or gid greater than this will not be stored, nor will a device file with a larger major or minor number. The exact behavior, which depends on your Solaris release (and SPARC vs x86), can be pathological but mostly things just silently fail and you don't find out until someone else discovers that some things you recovered from backups mysteriously don't work anymore.
I've only seen this once, but you'll be happy to know that there's a handy solution --one you can mix with another little used Solaris facility to truly throw yourself off the deep end of weird by embedding a call to pax within xargs:
% xargs -P -L 1 | pax -x xustar -w -f /dev/rmt/1mc
Will prompt the user for each file to be archived and store identifiers of almost any size.