Creating Hard link and Soft Links in Unix

 

Hard Link	Soft Link / symbolic  Link
If the inode entries are the same and if the count is 2 then they are hard linked.	if you see filename --> linked_directory Then its a symbolic link.
la –lia	ls -a
ln <source> <target file> (without the option –s which stands for soft link).	ln  -s <source> <target file> (with the option –s which stands for soft link).
It is essentially create identical copies, No matter  which one you update,  both of them will get updated
both links must reside on the same filesystem, the source file must exist	that are not applicable to softlinks (source and target can be on seperate file systems, source does not have to exist, etc.) additional I/O necessary to complete file access, additional storage taken up by softlink file's data
	A "soft" link does not increase the inode count for the referenced file, a "hard" link does. If the count = 1, it's a soft link. If the count is > 1, it's a hard link.

Example of Viewing existing Hard link

ls –lia

1. Same iNode number  : 245787
2.  After permission column it lists 2

oracle@test:/app/oracle/product/11.2.0.3/grid/network/admin $ ls -lia total 120 153544 drwxr-xr-x   4 oracle     dba           1024 Sep 12 04:27 ./ 153543 drwxr-xr-x  11 oracle     dba           1024 Aug 27 17:39 ../ 250089 drwxr-xr-x   2 oracle     dba           1024 Oct 17 12:58 OLD/ 167535 -rw-r--r--   1 oracle     dba           1580 Sep  4 05:01 listener.old 153001 -rw-r--r--   1 oracle     dba           4524 Oct 17 13:01 listener.ora 159439 -rw-r--r--   1 oracle     dba            205 May 11  2011 shrept.lst 167531 -rw-r--r--   1 oracle     dba            881 Aug 27 18:17 sqlnet.ora 245787 -rw-r--r--   2 oracle     dba          43224 Sep 25 01:38 tnsnames.ora oracle@test:/app/oracle/product/11.2.0.3/grid/network/admin $ cd $TNS_ADMIN oracle@test:/app/oracle/product/11.2.0.3/db/network/admin $ ls -lia total 102 168564 drwxr-xr-x   4 oracle     dba           1024 Sep  7 00:29 ./ 168563 drwxr-xr-x  11 oracle     dba           1024 Aug 27 18:11 ../ 158839 drwxr-xr-x   2 oracle     dba           1024 Sep 25 01:35 OLD/ 164004 -rw-r--r--   1 oracle     dba           2690 Sep  7 00:29 listener.ora 168565 drwxr-xr-x   2 oracle     dba             96 Aug 27 18:00 samples/ 178592 -rw-r--r--   1 oracle     dba            205 May 11  2011 shrept.lst 245790 -rw-r--r--   1 oracle     dba            881 Aug 27 18:17 sqlnet.ora 245787 -rw-r--r--   2 oracle     dba          43224 Sep 25 01:38 tnsnames.ora

Example of viewing SoftLink

oracle@test1:/app/grid/product/11.2.0.3/network/admin $ ls -lia total 82    343 drwxr-xr-x   4 oracle     dba           1024 Aug 24 17:01 ./    342 drwxr-xr-x  11 oracle     dba           1024 Aug  9 09:55 ../ 16349 drwxr-xr-x   2 oracle     dba           1024 Sep  7 12:43 OLD/ 12489 -rw-r--r--   1 oracle     dba            186 Aug  9 10:26 endpoints_listener.ora 12165 -rw-r--r--   1 oracle     dba           1568 Sep  7 12:46 listener.ora 12488 -rw-r--r--   1 oracle     dba            534 Aug  9 10:26 listener.ora.bak.usfspfd1 12477 -rw-r--r--   1 oracle     dba            368 Aug  9 10:26 listener12080910AM2605.bak    344 drwxr-xr-x   2 oracle     dba             96 Aug  9 09:49 samples/   5108 -rw-r--r--   1 oracle     dba            205 May 11  2011 shrept.lst 22677 -rw-r--r--   1 oracle     dba            561 Aug 13 18:33 sqlnet.ora 12487 -rw-r--r--   1 oracle     dba            646 Aug  9 10:26 sqlnet.ora_temp 22674 -rw-r--r--   1 oracle     dba          29904 Aug 23 16:09 tnsnames.old  42504 lrwxr-xr-x   1 oracle     dba             58 Aug 24 17:01 tnsnames.ora@ -> /app/oracle/product/11.2.0.3/db/network/admin/tnsnames.ora oracle@test1:/app/grid/product/11.2.0.3/network/admin $ cd $TNS_ADMIN oracle@test1:/app/oracle/product/11.2.0.3/db/network/admin $ ls -lia total 82 150342 drwxr-xr-x   4 oracle     dba           1024 Aug 21 16:29 ./ 150341 drwxr-xr-x  11 oracle     dba           1024 Aug  9 11:36 ../ 214228 drwxr-xr-x   2 oracle     dba           1024 Oct 30 22:55 OLD/ 268044 -rw-r-----   1 oracle     dba           3554 Aug 14 14:43 listener.ora 150343 drwxr-xr-x   2 oracle     dba             96 Aug  9 11:23 samples/ 170627 -rw-r--r--   1 oracle     dba            205 May 11  2011 shrept.lst 268082 -rw-r--r--   1 oracle     dba            561 Aug 14 14:50 sqlnet.ora 266832 -rw-r--r--   1 oracle     dba          32061 Oct  9 10:42 tnsnames.ora

Daily check on the database before business volume picks up

Session Count

SQL>     SELECT a.inst_id, COUNT (1) "Session Count"      FROM sys.gv_$session a     GROUP BY a.inst_id SQL> /    INST_ID Session Count ---------- -------------          1            67          2           105

Long Operation – Time Remaining is greater than Zero.

SQL> l     SELECT * FROM sys.gv_$session_longops     WHERE  TIME_REMAINING > 0

DBMS Jobs

SELECT job,        SUBSTR (what, 1, 30),        schema_user,        last_date,        next_date,        broken,        NVL2 (this_date, 'Y', 'N') running   FROM dba_jobs s ORDER BY schema_user, last_date

Buffer Gets

Replace the v.sql text with the frequent SQL statements important to your application.

SELECT v.inst_id,        ROUND (v.buffer_gets / v.executions, 1) avggets,        v.executions,        v.module,        SUBSTR (v.sql_text, 1, 60) querysql   FROM sys.gv_$sql v WHERE v.buffer_gets > 0    AND v.executions > 0    AND v.executions IS NOT NULL    AND DECODE (executions, 0, NULL, (v.buffer_gets / v.executions)) > 10    AND (v.sql_text LIKE 'FROM TBL_ABC%'      OR  v.sql_text LIKE 'FROM TBL_XYZ%')  ORDER BY v.inst_id, avggets DESC;

How to register a database to use RMAN catalog using OEM Grid 11g

 

1. Login Oracle Enterprise Manager.
2. Select Target –> Chose the database
3. Go Availability tab and click "Recovery Catalog Settings" under Backup/Recovery Setup.
4. Choose "Use Recovery Catalog" option.
5. Click "Add Recovery Catalog" button to add recovery catalog.
6. And fill required fields such as host, port,sid, username, etc

 

Moving Data files Between ASM Disk Groups

 

Method 1: Using RMAN

Step 1: Start RMAN and connect to the target database. $ rman target / Step 2: Generate a report that shows the names of the datafiles. RMAN> REPORT SCHEMA; Step 3:  Back up the datafile to the new ASM disk group. RMAN> BACKUP AS COPY DATAFILE '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421' FORMAT '+DG_DEVSYS_mydb1_DATA_01'; Step 4:  Bring the Datafile Offline alter database datafile '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421' offline Step 5: Point the control file to the newly created copy of the datafile RMAN> SWITCH DATAFILE '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421' TO COPY; Step 6:  Recover the renamed datafile RMAN> recover datafile '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767'; Step 7. Bring the datafile online. alter database datafile '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767' online Step 8. Delete the old datafile RMAN>DELETE DATAFILECOPY “DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421”

Reference: http://download.oracle.com/docs/cd/B28359_01/backup.111/b28270/rcmasmmi.htm

Method 2: Using ASMCMD CP ( Copy ) Command

Step 1: Start RMAN and connect to the target database. $ rman target / Step 2: Generate a report that shows the names of the datafiles. RMAN> REPORT SCHEMA; Step 3:  Bring the Datafile Offline alter database datafile '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421' offline Step 4:  Connect to ASMCMD and use CP to copy files $ asmcmd –p ASMCMD [+] > cp +DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421 +DG_DEVSYS_mydb1_DATA_01 Step 5:  After copied datafile, then rename file in database.  With ASM(OMF) this delete old datafile. alter database rename file '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421'  to '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767' Step 6:  Recover the renamed datafile RMAN> recover datafile '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767'; Step 7. Bring the datafile online. alter database datafile '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767' online Step 8: Verify the file name RMAN> REPORT SCHEMA

Method 3:  Using RMAN Copy

Step 1:  Restrict the Session ALTER SYSTEM enable restricted session; Step 2:   Bring the Datafile Offline alter database datafile '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421' offline Step 3: Start RMAN and connect to the target database. $ rman target / Step 4:  RMAN Copy datafile RMAN> copy datafile '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421' to '+DG_DEVSYS_mydb1_DATA_01'; Step 5:  After copied datafile, then rename file in database.  With ASM(OMF) this delete old datafile. alter database rename file '+DG_DEVSYS_mydb1_FLASH_01/mydb1/datafile/data01.290.709985421'  to '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767' Step 6:  Recover the renamed datafile RMAN> recover datafile '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767'; Step 7. Bring the datafile online. alter database datafile '+DG_DEVSYS_mydb1_DATA_01/mydb1/datafile/data01.272.764459767' online Step 8: Verify the file name RMAN> REPORT SCHEMA Step 9: Disable the Restricted Session ALTER SYSTEM disable restricted session;

Steps to set database on flashback mode in RAC for Oracle 11g

 

---- Check if flashback on?

SELECT flashback_on, log_mode FROM v$database;

--- Check for Flashback Parameters existing

set linesize 121 col name format a30 col value format a30 SELECT name, value FROM gv$parameter WHERE name LIKE '%flashback%';

---- Stop the RAC Database , it will stop all the instances of the DB

srvctl stop database -d sfodb

--- Start the DB in mount state

srvctl start instance -d sfodb -i sfo38u1 -o mount

-- Set the Flashback on

alter database flashback on;

--- Open the database

alter database open;

--- Start the remaining instances of the RAC

srvctl start instance -d sfodb -i sfo38u2 -o mount exclusive

-- Verify the flashback settings

select INST_ID,Name, FLASHBACK_ON from gv$database;