No Applications Can Run (‘Frozen’ System) 
At times you may find that your system has completely frozen. No application can proceed, unlike a slow running system. If this happens, it will usually happen abruptly. It is often the result of a resource being completely depleted, and the Oracle database system can no longer continue.
The most common reasons for a frozen system are:
Check whether the ARCH process is running (
You should monitor the archiving process on a regular basis to avoid the freezing of the system due to errors in this area. You can use the options provided by the CCMS (
Displaying Redo Log Backups: Oracle).
See also:
SAP Database Management: Oracle and the SAP notes database (for example, note number 391)
See also:
Database Message Log (Oracle)
Checkpoint Monitoring (Oracle) Exclusive Lockwaits (Oracle)