RE: Another Database Down

From: Robertson Lee - lerobe <lerobe_at_acxiom.co.uk>
Date: Thu, 24 May 2001 10:07:25 -0700
Message-ID: <F001.0030D946.20010524094139@fatcity.com>

<SPAN

class=281083816-24052001>From Metalink,
 
<FONT

face=Courier>  In Oracle releases before 7.3.3 on Unix it was possible for two instances to   mount the same database using different values for

ORACLE_SID when not  running in Parallel Server mode. This could cause 
database corruption  as two independent instances could then access the 
same database files  with no synchronisation between them. This problem 

is described in   <A
href="http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_id=272030&p_database_id=BUG" target=corner><FONT color=#000000 face=Courier size=2>[BUG:272030].Platforms /

Versions affected~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  This problem has 

never existed on VMS as a mount lock is always used.  This problem still exists on Windows NT at the time of writing.   It is possible that the problem still exists on some Unix platforms due   to <A href="http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_id=690938&p_database_id=BUG" target=corner><FONT color=#000000 face=Courier size=2>[BUG:690938] (Eg: The LK
file does not work on HPUX releases   7.3.3 - 8.0.X )  What is the LK<dbname> file

?~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  To prevent this from occurring on 

Unix systems a 'mount lock' file was   introduced in Oracle 7.3.3. This zero length lock file is created in the   '$ORACLE_HOME/dbs' directory with the name 'lk<DBNAME>'.   Now when Oracle tries to MOUNT

a database:	1. The DB_NAME parameter is used to complete the filename. 
	   Eg: If DB_NAME=V803 then the filename is 
"$ORACLE_HOME/dbs/lkV803"	2. If this file does not exist it is created. 
	   If the file does exist it is opened.	   	3. 

The file is locked using an exclusive Unix file lock.  If any of these steps fail then the MOUNT operation is not allowed and  and ORA 1102 ("cannot mount database in EXCLUSIVE mode") is signaled.Implications if Upgrading from Earlier

Releases~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~  Prior to 

this change it was possible to have two databases running from   the same $ORACLE_HOME that had the same DB_NAME but different $ORACLE_SIDs.  This is no longer allowed - Oracle recommends that in such cases one of  the databases has its database name changed. This can be achieved using the  CREATE CONTROLFILE command as described in
<A

href="http://metalink.oracle.com/metalink/plsql/ml2_documents.showDocument?p_id=1012929.6&p_database_id=NOT" target=corner><FONT color=#000000 face=Courier size=2>[NOTE:1012929.6] . Once
the  databases have different names they will each use their own 'lkDB_NAME' file.  Additional

Notes~~~~~~~~~~~~~~~~  1. Never remove the 'lkDB_NAME' file unless 

you are certain there is     no local instance using the database.  2. The 'lkDB_NAME' file may exist even when the database is shut down so     its presence cannot be used as an indication that the database is      in use.  3. Some notes may erroneously report the file name to be 'lk<SID>' rather     than 'lk<DB_NAME>'. In many cases the SID and DB_NAME are the same but     it is important to note that the filename uses the DB_NAME and NOT      the SID.  4. Possible errors from the

locking code include:		ORA-9992 scumnt: failed to open 


<FILENAME>  		ORA-9993 scumnt: failed to lock 

<FILENAME>  		ORA-1102 cannot mount database in EXCLUSIVE 

mode
 

  <FONT face=Tahoma
  size=2>-----Original Message-----From: Burton, Laura L.   [mailto:BurtonL_at_prismplus.com]Sent: 24 May 2001 15:57To:   Multiple recipients of list ORACLE-LSubject: RE: Another Database   Down
  No,
  I did not know about this.  Could you explain or tell me where I can find   info on this?
  <FONT color=#0000ff face=Arial
  size=2> 
  <FONT color=#0000ff face=Arial
  size=2>Laura   

    <FONT face="Times New Roman"
    size=2>-----Original Message-----From: Robertson Lee - lerobe     [mailto:lerobe_at_acxiom.co.uk]Sent: Thursday, May 24, 2001 3:51     AMTo: Multiple recipients of list ORACLE-LSubject: RE:     Another Database Down
    <SPAN
    class=421544407-24052001>Have you tried removing/moving the     lk<ORACLE_SID> file in the $ORACLE_HOME/dbs directory     ??
    <SPAN
    class=421544407-24052001> 
    <SPAN
    class=421544407-24052001>Lee     

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