On AIX, and UNIX in general, DB2 instance creation fails with vague errors:

Update DBM cfg SYSADM_GROUP errcode = 8DBI1281E The database manager configuration file could not be           initialized.  Explanation: An error occurred when attempting to initialize the database manager configuration file. A DB2 instance could not be created or migrated.  

One of the main reasons for DB2 instance creation to fail is that it is unable to resolve the hostname of the machine. Under the covers, DB2 instance creation would create a TCP/IP Service. It fails to do so if the hostname of the machine can’t be resolved. But instead of throwing an understandable message informing the user the same, it throws the above vague/ambiguous error.

So the tip here is to run the command host and make sure the host is resolved before creating a DB2 instance.

For new UNIX users, the below info shows how to run the command host.

• Command: host ‘short hostname of the machine’
• Successful Result : the host should be resolved to an IP.
• Failure Case: If host can’t be found, make sure the file /etc/resolv.conf exists with all the needed info.