I'm trying to make a shell script that will allow the users to backup an Informix IDS database before using it and rollback (restore it) if they need to do so.
I know I can use ontape and onbar but I don't know if it would work for every database, no matter the size, and to be honest, I don't know if it would be safe for the users to use a script that takes the DBNAME as an argument to backup/restore.
Using ON-Tape (ontape), you can back up a whole server, but not a single database. Using ON-Bar (onbar), you can back up one or more storage spaces (dbspaces, blobspaces, etc) or the whole server. Therefore, if you locate the database in a separate dbspace and ensure no other database uses the dbspace, then you can use ON-Bar to achieve a database-level backup. Consequently, you must design your system to allow for database recovery and restore.
Running backups requires administrative privileges, which you should not give to anyone casually. Therefore, you will need to design a backup and restore system that will limit people to backing up the databases you intend them to be able to backup. I have some views on how this can be done, but the result is complex.
Amongst other places, read the Comparison of the ON-Bar and ON-Tape utilities. That is part of the Backup and Restore Guide documentation.