Locks are used to protect the data or resourses from the simulteneous use of them by multiple sessions which might set them in inconsistant state… Locks are external mechanism, means user can also set locks on objects by using various oracle statements.

Latches are for the same purpose but works at internal level. Latches are used to Protect and control access to internal data structres like various SGA buffers.They are handled and maintained by oracle and we can’t access or set it.. this is the main difference

ASM Limitation

ASM has the following size limits:
• 63 disk groups in a storage system
• 10,000 ASM disks in a storage system
• 1 million files for each disk group

How to Detect and Mount the CD-ROM in Linux

1. Detecting CD-ROM/DVD-ROM drive
# wodim –devices

[lokesh@Mudhalvan ~]$ wodim –devices
wodim: Overview of accessible drives (1 found) :
————————————————————————-
0 dev=’/dev/scd0′ rwrw– : ‘HL-DT-ST’ ‘RW/DVD GCC-4243N’
————————————————————————-
[lokesh@Mudhalvan ~]$

2. Testing for iso9660 compatibility
# cat /proc/filesystems

3. Creating mount point
# mkdir /media/cdrom

4. Mounting CD
# mount -t iso9660 /dev/scd0 /media/cdrom/

5. Altering /etc/fstab
/dev/sdc0 /media/cdrom iso9660 ro,user,noauto 0 0

6. Unmount and eject CD
# unmout /dev/sdc0
# eject

1. Login as root and do ioscan before add the Lun to the Unix Machine
# ioscan -fnCdisk

2. Add the lun to Unix machine by EMC Navigator

3. No need to restart the Unix machine do the ioscan again will show you the newly added disk as CLAIMED but devices will not show

#ioscan -fnCdisk

How to Drop Dbconsole and repository – Enterprice Manager in 10g
emca -deconfig dbcontrol db -repos drop

Enter the following information:
Database SID: AARTHI
Listener port number: 1521
Password for SYS user:
Password for SYS user: password
Do you wish to continue? [yes(Y)/no(N)]: Y
Apr 11, 2010 7:47:37 AM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at C:\oracle\product\10.2.0\db_1\cfgtoollog
s\emca\aarthi\emca_2010-04-11_07-47-10-AM.log.
Apr 11, 2010 7:47:41 AM oracle.sysman.emcp.EMDBPreConfig performDeconfiguration
WARNING: EM is not configured for this database. No EM-specific actions can be p
erformed.
Apr 11, 2010 7:47:42 AM oracle.sysman.emcp.EMReposConfig dropRepository
INFO: Dropping the EM repository (this may take a while) …
Apr 11, 2010 7:48:07 AM oracle.sysman.emcp.EMReposConfig invoke
INFO: Repository successfully dropped
Enterprise Manager configuration completed successfully
FINISHED EMCA at Apr 11, 2010 7:48:07 AM

How to Create Dbconsole – Enterprice Manager in 10g

emca -config dbcontrol db -repos create
C:\Documents and Settings\user1>emca -config dbcontrol db -repos create

STARTED EMCA at Apr 11, 2010 7:52:24 AM
EM Configuration Assistant, Version 10.2.0.1.0 Production
Copyright (c) 2003, 2005, Oracle. All rights reserved.

Enter the following information:
Database SID: AARTHI
Listener port number: 1521
Password for SYS user:
Password for DBSNMP user:
Password for SYSMAN user:
Email address for notifications (optional): aarthimudhalvan@gmail.com
Outgoing Mail (SMTP) server for notifications (optional): smtp.gmail.com
—————————————————————–

You have specified the following settings

Database ORACLE_HOME ……………. C:\oracle\product\10.2.0\db_1

Database hostname ……………. lokesh.fletsphone
Listener port number ……………. 1521
Database SID ……………. AARTHI
Email address for notifications …………… aarthimudhalvan@gmail.com
Outgoing Mail (SMTP) server for notifications …………… smtp.gmail.com

—————————————————————–
Do you wish to continue? [yes(Y)/no(N)]: Y
Apr 11, 2010 7:53:44 AM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at C:\oracle\product\10.2.0\db_1\cfgtoollo
s\emca\aarthi\emca_2010-04-11_07-52-24-AM.log.
Apr 11, 2010 7:53:57 AM oracle.sysman.emcp.EMReposConfig createRepository
INFO: Creating the EM repository (this may take a while) …

How to recreate Dbconsole repository – Enterprice Manager in 10g
emca -config dbcontrol db -repos recreate

===== ORA-13516: AWR Operation failed: INTERVAL Setting is ZERO

The above error message is because of the INTERVAL of snapshot setting is Zero. You can change the snapshot setting by using the following command. The below command set the interval to 60 mins

DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS( INTERVAL=>60 );

exec DBMS_WORKLOAD_REPOSITORY.create_snapshot();

* V$ACTIVE_SESSION_HISTORY – Displays the active session history (ASH) sampled every second.
* V$METRIC – Displays metric information.
* V$METRICNAME – Displays the metrics associated with each metric group.
* V$METRIC_HISTORY – Displays historical metrics.
* V$METRICGROUP – Displays all metrics groups.
* DBA_HIST_ACTIVE_SESS_HISTORY – Displays the history contents of the active session history.
* DBA_HIST_BASELINE – Displays baseline information.
* DBA_HIST_DATABASE_INSTANCE – Displays database environment information.
* DBA_HIST_SNAPSHOT – Displays snapshot information.
* DBA_HIST_SQL_PLAN – Displays SQL execution plans.
* DBA_HIST_WR_CONTROL – Displays AWR settings.

$cd ORACLE_HOME
$cd rdbms
$cd admin
$sqlplus /nolog
SQL>connect / as sysdba
SQL>@awrrpt.sql
Current Instance
~~~~~~~~~~~~~~~~

DB Id DB Name Inst Num Instance
———– ———— ——– ————
XXXX TEST 1 test

Specify the Report Type
~~~~~~~~~~~~~~~~~~~~~~~
Would you like an HTML report, or a plain text report?
Enter ‘html’ for an HTML report, or ‘text’ for plain text
Defaults to ‘html’
Enter value for report_type:html
Type Specified: html
Instances in this Workload Repository schema
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DB Id Inst Num DB Name Instance Host
———— ——– ———— ———— ————
* XXXXX 1 TEST test XXXXXX

Using XXXXX for database Id
Using 1 for instance number
Specify the number of days of snapshots to choose from
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Entering the number of days (n) will result in the most recent
(n) days of snapshots being listed. Pressing without
specifying a number lists all completed snapshots.
Enter value for num_days:1
Enter value for num_days: 1
Listing the last day’s Completed Snapshots
Snap
Instance DB Name Snap Id Snap Started Level
———— ———— ——— —————— —–
test TEST 10401 24 Mar 2010 00:00 1
10402 24 Mar 2010 01:00 1
10403 24 Mar 2010 02:00 1
10404 24 Mar 2010 03:00 1
10405 24 Mar 2010 04:00 1
10406 24 Mar 2010 05:00 1

Specify the Begin and End Snapshot Ids
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Enter value for begin_snap: 1405
Begin Snapshot Id specified: 1405

Enter value for end_snap: 1406
End Snapshot Id specified: 1406

Specify the Report Name
~~~~~~~~~~~~~~~~~~~~~~~
The default report file name is awrrpt_1_10405_10406.html. To use this name,
press to continue, otherwise enter an alternative.

Enter value for report_name:awrrpt_1_10405_10406.html

This will generate a report into the current folder with “awrrpt_1_10405_10406.html” name

exec DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS( INTERVAL=>0 );

select * from DBA_HIST_WR_CONTROL

DBID SNAP_INTERVAL RETENTION TOPNSQL
1898043910 +40150 00:00:00.000000 +07 00:00:00.000000 30