These sequencial numbers items should be journal receivers
You should back them up before deleting them.
Journal receivers contain a history of changes to tthe jorunaled physical files or access paths and can be used to recover data.
If QDBJRN is also a receiver, the same rules apply but if it’s the “journal” do not delete it.
The journal contains the rules for journaling not the data.
If you are at V5R2 or later, these might be okay to delete; otherwise, no, these should <b>not</b> be deleted and you might not be allowed to delete them. One related example quote from the V5R4 Info Center : “You should not use the library <b>QRECOVERY</b> because it is intended for system use only. The library <b>QRECOVERY</b> contains objects that the system needs to operate properly.”
The name alone should warn you off when you’re not <i>certain</i> about the consequences.
In this case, none of the objects are “files” nor are they “backups”. QDBJRN was a journal for the system database cross-reference files. I <i>think</i> QDBJRN is not used after V5R1.