What will happen if oracle unable to write Alertlog, Core Dump Or Tracefiles

In this I will show what can happen if Oracle is unable to write to the trace/alert.log to bdump or cdump & udump directories. It can happen if you loss your background_dump_dest or user_dump_dest or core_dump_dest ormay the the partition containing bdump or udump folder is full.

The answer is if oracle is unable to write to the trace/alert.log to bdump & udump directories then the oracle behavior depends on which process is attempting to write to alert.log/trace/coredump file. Based on the process the instance may or may not crash immediately.

If a foreground process corresponding to user process wants to write, but is unable to do so, the process may hang/terminate but there will not be any impact on database.

But if the background process wants to write it may hang and eventually crash the instance if that background process terminates.

In the following section I demonstrate this behavior on 10.2g

1.Start database with spfile Create one bdump directory
SQL> !mkdir /oradata2/bdump

2.Set the background_dump_dest to this location.
SQL> alter system set background_dump_dest='/oradata2/bdump';
System altered.

SQL> show parameter background_dump_dest
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
background_dump_dest string /oradata2/bdump

3.Switch logfile. It will generate one trace file in the background_dump_dest.
SQL> alter system switch logfile;
System altered.

SQL> !ls /oradata2/bdump
arjudba_arc0_10688.trc

4.Move the bdump location to a new location. Here bdump_bak.
SQL> !mv /oradata2/bdump /oradata2/bdump_bak

SQL> !ls /oradata2/bdump
/oradata2/bdump: No such file or directory

5.Now you may face one of two scenario a) or b).

a)If database is open then Instance will crash
SQL> alter system switch logfile;
System altered.

SQL> alter system switch logfile;
alter system switch logfile
*
ERROR at line 1:
ORA-03113: end-of-file on communication channel

b)If database is shutdown startup will fail with ORA-00444 and ORA-07446.
SQL> shut immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL> startup
ORA-00444: background process "MMAN" failed while starting
ORA-07446: sdnfy: bad value '' for parameter .

So if you try to write alert log file while instance is up and running it may fail and eventually crush the instance.

However, for a foreground process the database will not crash, if it is unable to write to alert.log.