Juan Martín: de la ayuda de informix:
`
The database server cannot create a temporary disk file. The file
should be created in the directory that the DBTEMP environment variable
specifies (or /tmp by default on UNIX systems). Check the accompanying
ISAM error code and look for operating-system error messages that
might give more information. Possibly your account does not have write
permission in that directory, or the disk is full. Since Version 5.01,
the INFORMIX-SE database server uses the DBTEMP environment variable,
but Informix Dynamic Server and INFORMIX-OnLine Dynamic Server do not.
On a UNIX system, try increasing the maximum number of open files
(NFILES parameter on some systems) to approximately 400.
`
Hay que revisar la configuración de tu servidor Informix. Hay que probar agregando un dbspace del tipo temporal y especificarlo en el onconfig.