The software uses a mechanism to access data involving an Object Management System (OMS). This system manages the information needed to access data in the DTECT_DATA directories or from other data stores. This access information is stored in a separate "meta"-datastore.

The OMS uses a flat file approach to store this access information. Compared to a 3rd party database this has the advantage of simplicity, independence of extra systems to manage, and transparency. On the downside, however:

The file permissions must be right; users of the software must have read and write access to the survey directories and files.

The system is probably less robust in the presence of file system trouble.

If you have no write access to the survey directory, you will experience the problem that newly created entries in the system are not persistent, meaning you cannot 'see' them anymore after creation. Sometimes this is good enough, e.g. when you need a SEG-Y dump to tape you may not need the entry afterwards. But usually, this is not acceptable. Therefore, get the permissions right. If you're working in a team, read the sharing strategy question.

In the case of file system trouble, one or more of the information storage files '.omf' in the survey directory, or in one of the survey's subdirectories may be damaged. If the main .omf is damaged, you will usually not even be able to reach Surfaces, Seismics, etc. subdirectories from within the software. If a subdirectory's .omf is damaged, you may be unable to reach a type of object.

In any case, you'll have to find out which .omf causes the trouble. In general, if something damages your .omf, you'll have to put a backup back in place. You may first try to rename .omf to .omf.damaged ('mv .omf .omf.damaged'). the OMS will try to read a .omf, and if there is none it will try the back-up '.omb' . If it finds that, it will proceed as if nothing happened.

Because the .omf in the survey root is so important, you may want to give extra protection to its .omf by making .omf read-only. Of course, you can do this with the '.omf' in the survey directory itself, not in the .omf files in the subdirectories.