The database you tried to open is not visible to the database server. Check the spelling of the name. Possibly the database is located in a different database server (or network system), and you have omitted to specify the server name (or site name) with the database name. If you are sure the database should exist just as you spelled it, your next step depends on the database server you are using.
If you are using IBM Informix SE, the visible databases are directories with names in the form dbname.dbs. You must be able to read from and write to them. The database server looks first in the current working directory and then in each directory named in the DBPATH environment variable. The most common cause of this error is an incorrect setting or no setting for the DBPATH environment variable.
If you are using IBM Informix Dynamic Server, IBM Informix Universal Server, or IBM Informix OnLine Dynamic Server, the database does not exist as you spelled it. In some environments, two or more instances of the database server can run at once and each instance has its own collection of databases. For Version 6.0 and later, the value of the INFORMIXSERVER environment variable determines the instance of the database server that you use. For Versions 5.1x and earlier, the ONCONFIG environment variable points to the configuration file that determines the instance. See your database server administrator if you think you might be using the wrong instance.
If you are connected to a secondary database server, the database you tried to open might exist, but is not logged. Databases are required to be logged to be able to access them on secondary database servers.