Hi,
Joblogs are stored on a filesystem not in the SAP database.
The problem will probably be there.
Possible reasons are :
1/
The filesystem used to store the joblogs is full.
2/
You are running multiple application servers on different host and the global filesystem containing the joblogs is not mounted on every host.
3/
The SAP system is refreshed or moved to another host and the global filesystem containing the joblogs was not copied.
4/
Someone deleted the joblogs in the filesystem ! ! !
Filesystem (directory) on UNIX where you will find the joblogs is :
/sapmnt/<SYSID>/global/xxxJOBLG
Replace <SYSID> with your system ID and xxx by the client.
On the global fileystem there is a directory per client containing the joblogs.