Hi Rodel,
SAPMNT<sys> directory is nearly full
Make sure SAP standard & reorganization jobs has already been scheduled in your system.You could refer SAP Note 16083 - Standard jobs, reorganization jobs.
You need to check for standard jobs by following the mentioned SAP note to resolve such type of issues.
Additionally you could refer SCN doc at File system is full – what need to be done?
Hope this will help you.
Regards,
Gaurav