We're using db2 9.5 and on rare occasions get the following error when attempting to connect to the database. The program is forked from another process and trying a second time always succeeds.
[IBM][CLI Driver] SQL30082N Attempt to establish connection failed with security reason "26" ("SERVER SECURITY PLUGIN ERROR"). SQLSTATE=08001
We use Kerberos, password-less authentication.
Seems like a problem with Kerberos or the authentication plugin. If everything seems fine you should also look for the problem in the network. Maybe db2 on this occasions cannot contact the kerberos and fails with this error.