DB2 get_help

db2 ?
db2 ? some_command
db2 ? options
db2 ? help
db2 ? error_code

for example:
> db2 crocodile
DB21034E  The command was processed as an SQL statement because it was not a
valid Command Line Processor command.  During SQL processing it returned:
SQL1024N  A database connection does not exist.  SQLSTATE=08003
> db2 ? SQL1024N

SQL1024N A database connection does not exist.

Explanation:  There is no connection to a database.  Other SQL
statements cannot be processed unless an SQL CONNECT was
previously executed.

The command cannot be processed.

User Response:  If the error occurred when disconnecting from the
database, continue processing.  If the error occurred on another
SQL statement, issue an SQL CONNECT statement and resubmit the
command or statement.

sqlcode:  -1024

sqlstate:  08003

Another way to get help fast is to copy/paste the error string into google (internet search engine). Especially Google Groups is very helpful. You usually get the answer on the very first screen.