What is the $ORACLE_HOME/dbs/hc_<ORACLE_SID>.dat file

1.What is the $ORACLE_HOME/dbs/hc_.dat file?

   The $ORACLE_HOME/dbs/hc_.dat is created for the instance health check monitoring.  It contains information used to monitor the instance health and to determine why it went down if the instance isn't up. The file will be recreated at every instance startup.

2. What happens if the $ORACLE_HOME/dbs/hc_.dat file is deleted?

    if you replace the file with an empty "dummy" copy, you will get an ORA-7445 error.  Therefore, if the file gets deleted on the fly while the database is up, or if the file is replaced with a 0 byte file, simply delete the file and restart the database.  The file will be correctly recreated at the next database startup. 

3.HP-UX Itanium  RAC 10.2.0.4   
  
   bug no.:7235094
  

PROBLEM:
--------
racgimon has file handle leak on healthcheck file. 
At the customer's site, ServiceGuard detected Split Brain then a node was bounced.
At that time, "ORA-27301: OS failure message:
File table overflow" was recorded on alert.log. Also, "glance" showed that racgimon was opening more than 26,000 filehandles. The racgimon process was started around 20 days ago(14th Jun). Due to the handle leak by racgimon, the operating system was exhausting the kernel limit for maximum opened files ("nfile" on HP-UX).

tail -f   "$ORACLE_HOME/log/< NodeName>/racg/imon_< InstanceName>.log"
2008-07-04 16:16:24.707: [RACG][20] [25433][20][ora.r1024.r10241.inst]:

  GIMH: GIM-00104: Health check failed to connect to instance. 
  GIM-00090: OS-dependent operation:mmap failed with status: 12 
  GIM-00091: OS failure message: Not enough space 
  GIM-00092: OS failure occurred at: sskgmsmr_13

At last, it exceeded "nfile" on HP-UX and ServiceGuard, Oracle, or any other applications could not run normally.

 

What Is The $ORACLE_HOME/dbs/hc_.dat File?
	:	390474.1	Type:	HOWTO
	Modified Date :	09-SEP-2008	Status:	PUBLISHED