DB2 fix - SQL6048N A communication error occurred during START or STOP DATABASE MANAGER processing.

Question: I attempted to complete a db2start on on a DB2 10.1.5 on Linux recently and this was the error returned.The DB2 instance did not start

03/10/2016 09:22:14     0   0   SQL6048N  A communication error occurred during START or STOP DATABASE MANAGER processing.
SQL1032N  No start database manager command was issued.  SQLSTATE=57019

What does this error mean and how can I fix the error to allow the DB2 instance starts?

Answer:   By coincidence , I had a similar problem recently when migrating a server to a test laboratory. As part of the migration the server administrator changed the hostname.

This was the first clue. When a DB2 instance starts up there is a check on the db2nodes.cfg file in the <INSTANCE_HOME>/sqllib/db2nodes.cfg .  

If a value comparison between the db2nodes.cfg and the value returned by the HOSTNAME are different , the error SQL6048N  A communication error occurred during START or STOP DATABASE MANAGER processing is returned.

You'll need to change the value in db2nodes.cfg, Typically this would be :

su - myInstance
cd <INSTANCE_HOME>/sqllib/
cp db2nodes.cfg db2nodesOriginal.cfg
vi db2nodes.cfg

Don't forget to use a fully qualified name (FQDN) if the system hostname is a FQDN

Read more on db2start

db2start at start up on Linux - DBA DB2

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SQL5043N Support for one or more communications protocols