When you create a database, the database server creates the following four dbspaces:
Dbspace name  | 
Purpose  | 
Default operating system file name  | 
|---|---|---|
IQ_SYSTEM_MAIN  | 
Main (permanent) IQ store file  | 
dbname.iq  | 
IQ_SYSTEM_MSG  | 
Message log file  | 
dbname.msg  | 
IQ_SYSTEM_TEMP  | 
Temporary IQ store file  | 
dbname.iqtmp  | 
IQ_SHARED_TEMP  | 
Temporary IQ store  | 
Initially, this dbspace contains no files.  | 
SYSTEM  | 
Catalog store file  | 
dbname.db  | 
The SYSTEM dbspace contains the system tables, which hold the schema definition as you build your database. It also holds a separate checkpoint log, rollback log, and optionally a write file, transaction log, and transaction log mirror, for the catalog store.
In addition to these database files, the database server also uses a temporary file to hold information needed during a session. This temporary file is not the same as the IQ temporary store, and is not needed once the database server shuts down. The file has a server-generated name with the extension .tmp. Its location is determined by the TEMP environment variable, or the coordinator environment variable on UNIX.