How to check if the OLAP option is installed in the database

select comp_name, version, status from dba_registry  where comp_name like '%OLAP%' order by 1 DESC;

Typical output if OLAP is installed:

COMP_NAME	VERSION	STATUS
Oracle OLAP API	11.2.0.4.0	VALID
OLAP Catalog	11.2.0.4.0	VALID
OLAP Analytic Workspace	11.2.0.4.0	VALID

You can also use:

select * from v$option where parameter='OLAP';

PARAMETER	VALUE
OLAP	TRUE

How to manually register the database with the listener

Sometimes there may be a delay before pmon register itself with the listener.

lsnrctl status will show

The listener supports no services
The command completed successfully

To manually force pmon to register, execute

alter system register;

How to handle RMAN DUPLICATE: Errors in krbm_getDupCopy during duplicate

I recently cloned a 11.2.0.4 database using tape backups as source.

The clone failed right before "open resetlogs". In other words, the database was restored and recovered, but DUPLICATE didn't succeed in opening it. So I did it manually, by recreating the controlfile using a template from the source database, and adjusted for the file layout on the auxiliary. The database opened nicely.

However, later during the day, the application team found that a new clone was needed due to some synch issue caused by a third-party replication tool. In other words, the entire database had to be copied from the latest version of our incremental level 1 backups and restored all over again.

No problem.

As usual, I started by saving away the spfile, password file and the block change tracking file located in $ORACLE_HOME/dbs. Following that, I mounted and dropped the database. All the files were automatically removed from disk by Oracle, and the instance terminated, as expected.

As I started to clone, I noticed some new messages in the alert log of the auxiliary database:

RMAN DUPLICATE: Errors in krbm_getDupCopy
Errors in file /u01/oracle/product/11204/admin/testdb01/diag/rdbms/testdb01/testdb01/trace/testdb01_ora_22544486.trc:
ORA-19625: error identifying file /u02/oradata/testdb01/system01.dbf
ORA-27037: unable to obtain file status
IBM AIX RISC System/6000 Error: 2: No such file or directory
Additional information: 3

This error was repeated for every data file in the database and appended to the same trace file as in the message above.

I found the errors worth checking.

Fortunately, these errors can be ignored. MOS Doc ID 1476641.1 "RMAN DUPLICATE: Errors In Krbm_getDupCopy found in alert.log" explains

"This happens after a previous failed duplicate trial, if the files copied to auxiliary destination have been deleted."

and


"The messages in alert.log indicate that rman cannot use a previous datafile copy for those files and that the files must be copied again to auxiliary destination. Duplicate checks if there are datafile copies already created by a duplicate to avoid restoring the files again.

So this is a part of Oracle restore optimization concept:

"...from 11.2 RMAN always checks if the file copy exists at destination hosts to avoid copying it again"


Great, but how does RMAN do that?

"If duplicate fails between the first restore/copy and the zeroing of the dbid, a second duplicate will find the _rm_dup_@.dat file and the clone default channel will read it into memory, once determined the name of the datafilecopy to be created by the second duplicate it is compared with the existing datafilecopy from the previous duplicate. If the datafilecopy still exists and matches the vital information of the datafile (file number, database id, creation scn, database name) and its checkpoint scn is behind the until scn then the datafilecopy can be used by this new duplicate and restore/copy isnot necessary"


The solution is simple:

"As files have already been deleted from auxiliary destination, ignore those messages."

I could also have followed the following advice:

"If you don't want to see those messages in alert.log but datafiles have already been deleted, on Auxiliary host, delete the file $ORACLE_HOME/dbs/_rm_dup_.dat where dup_db is the name of the clone instance."

How to drop a redo logfile group and redo logfile group members - syntax

alter database drop logfile group 4;

The drop statement will be confirmed by an entry in the database's alert log.

Don't forget to physically remove the file from disk afterwards.

You can also drop individual Group members:

alter database drop logfile member '/u03/oradata/proddb01/red04a.log';

Pay attention to the restrictions when dropping redo log groups and redo log members!

A good Query for redo log file information can be found here

Query to find basic redo log information

COL MEMBER FORMAT A50
SET LINES 200
SELECT A.GROUP#,A.MEMBER, B.BYTES/1024/1024 "MB", B.ARCHIVED,B.STATUS,B.SEQUENCE#
FROM V$LOGFILE A INNER JOIN  V$LOG B ON A.GROUP# = B.GROUP#
ORDER BY GROUP# ASC;

Result:

GROUP#	MEMBER	MB	ARCHIVED	STATUS	SEQUENCE#
1	/u04/oradata/proddb01/log1a.ora	1024	YES	INACTIVE	90510
1	/u04/oradata/proddb01/log1b.ora	1024	YES	INACTIVE	90510
2	/u04/oradata/proddb01/log2b.ora	1024	YES	INACTIVE	90511
2	/u04/oradata/proddb01/log2a.ora	1024	YES	INACTIVE	90511
3	/u04/oradata/proddb01/log3b.ora	1024	NO	CURRENT	90508
3	/u04/oradata/proddb01/log3a.ora	1024	NO	CURRENT	90508

How to add a comment on a column

Use this syntax:

COMMENT ON COLUMN SCOTT.EMP.DOB IS 'Date of Birth';

How to find the default tablespace type (smallfile vs bigfile)

SQL> select property_value 
from database_properties 
where property_name = 'DEFAULT_TBS_TYPE';

PROPERTY_VALUE
---------------
SMALLFILE

Change like this:

alter database set default bigfile tablespace;

The change will of course only take effect for future tablespaces, not existing ones.


Link to Oracle documentation