What does "**** GetLinuxConnectionNSS(Exit - Not found)" mean?

Periodically or sporadically, the follow message is seen in /var/log/messages :

    **** GetLinuxConnectionNSS(Exit-Not Found)

What do these mean or indicate?

These messages are more for information vs. indicating there is a problem.

Within NSS, there is a function named GetLinuxConnectionNSS().  This function resolves (or looks up) a linux uid in an internal hash table:

• If the uid is *not* found, the message, "**** GetLinuxConnectionNSS(Exit - Not found)", is logged to /var/log/messages.
• If the uid is found, the function returns other information for the user (such as GUID, etc.).
  In this case, there will be no data logged to /var/log/messages, only the information returned to the requesting process.
  

One, but not every, cause of this message can be due to a LUM-enabled user either getting removed from eDirectory or the uid being changed -- AND the old uid is an owner of files on the filesystem.  As the old uid is still an owner, and doesn't exist, the uid cannot be resolved to a name.