Far Sync (Oracle 12c New Feature)

Oracle Far Sync is an Oracle 12c new feature for Oracle Data Guard. This feature is meant to resolve the performance problems induced by network latency when you maintain a standby database geographically distant of the primary database. In this type of situation you sometimes have to make a compromise between performance and data loss. [...]

The post Far Sync (Oracle 12c New Feature) appeared first on Oracle DBA Scripts and Articles (Montreal).

How to Rename a Table

I tested this example in Oracle 12.1. First I created a table:

SQL> create table fred
  2  as select * from user_synonyms
  3  where 1 = 2
  4  /
 
Table created.

SQL>

Then I checked its object_id for later:

SQL> select object_id
  2  from user_objects
  3  where object_name = 'FRED'
  4  /
 
OBJECT_ID
----------
     92212

SQL>

... and described it:

SQL> desc fred
Name                       Null?    (more...)

Frequently Misused Metrics in Oracle

Lying Businessman

Back in March of last year I wrote an article on the five frequently misused metrics in Oracle: These Aren’t the Metrics You’re Looking For.

To sum up, my five picks for the most misused metrics were:

Business Graph

  1. db file scattered read – Scattered reads aren’t always full table scans, and they’re certainly not always bad.
  2. Parse to Execute Ratio – This is not a metric that shows how often you’re hard parsing, no matter how (more...)

RMAN Redundancy is not a Viable Retention Policy


Originally posted by me on the Pythian blog. This is an older post that I somehow forgot to post on my own blog, but another recent redundancy foul-up reminded me of it.

The story you are about to read is based on actual events. Names and paths have been changed to protect the innocent. I call this scenario “The Perfect Storm” because it took just the right combination of events and configurations. Sadly, this doesn’t (more...)

WordPress 3.8.3 – Auto Update

WordPress 3.8.3 came out yesterday. It’s a small maintenance release, with the downloads and changelog in the usual places. For many people, this update will happen automatically and they’ll just receive and email to say it has been applied.

I’m still not sure what to make of the auto-update feature of WordPress. Part of me likes it and part of me is a bit irritated by it. For the lazy folks out there, (more...)

ORA-12899

This was tested on Oracle 11.2. If you try to update a column with a value which is too long, you will get an ORA-12899:
 
SQL> conn andrew/reid
Connected.
SQL> create table tab1 (first_name varchar2(10))
  2  /
 
Table created.
 
SQL> insert into tab1 values ('Christopher')
  2  /
insert into tab1 values ('Christopher')
                         *
ERROR at line 1:
ORA-12899: value too large for column
"ANDREW"."TAB1"."FIRST_NAME" (actual: (more...)

Parallel Execution Skew – Demonstrating Skew

This is just a short notice that the next part of the mini-series "Parallel Execution Skew" is published at AllThingsOracle.com

Performance live discussion on twitter, 12pm PST Tue April 15

Confio software is hosting a live discussion on twitter tomorrow Tuesday April 15 at 12pm PST on the subject of Oracle performance.

I’ll be online answering performance questions and have invited many other friends to participate. Some friends who’ve said they’ll be there are

Participation and tracking of the discussion can accomplished by either posting with and  following along with the #datachat  hashtag.

Get (more...)

Don’t use %NOTFOUND with BULK COLLECT

I was working on a script for the ultimate RMAN backup validation and hoping to submit the article for an Oracle conference.

To my chagrin, one version of the script was failing for one condition and the other version would failed for another condition.

Basically, the script was very buggy.

The objective is to create a RMAN script to validate 8 backupset at a time.

I decided to use Bulk Collect and Limit clause.

Currently (more...)

From Las Vegas to Ottawa

After a very engaging session at Collaborate14 in sunny Las Vegas amidst the desert of Nevada, I just arrived in not-so-bitterly cold Ottawa, the capital of Canada. Looking forward meeting with various Pythian colleagues and hanging out with the friends I cherish most.

My Exadata IORM session went well. Lots of follow back discussion plus questions are still pouring in. I promise I will answer them as soon as I return to Australia after couple (more...)

An accusatory error message

I found this hilarious

SQL> startup
ORACLE instance started.

Total System Global Area 1469792256 bytes
Fixed Size                  2402776 bytes
Variable Size             536872488 bytes
Database Buffers          922746880 bytes
Redo Buffers                7770112 bytes
Database mounted.
ORA-19821: an intentionally corrupt log file was found

Really ? I intentionally corrupted my log file ?  I dont think so !

:-)


SQL injection

Another big public username and password leak…

http://o.canada.com/technology/bell-canada-security-breach-391451/

Some good reading on how it was done, and thus ensuring your code isn’t prone to SQL injection here:

http://www.troyhunt.com/2014/02/heres-how-bell-was-hacked-sql-injection.html


Pluggable database and restricted sessions

Once you get into pluggable database territory, you might need to check your usage of "alter system enable restricted session", because unless you’ve patched, there’s a little bug which lets you enable restricted session, but wont let you get out of it ! :-)

For example:

SQL> alter session set container = pdb12;
 
Session altered.
 
SQL> alter system enable restricted session;
 
System altered.
 
SQL> select logins from v$instance;
 
LOGINS
----------
RESTRICTED
 
SQL> alter system disable restricted  (more...)

OUGN 2014

I had the pleasure of being a guest of the Norwegian User Group for the second year in a row on their famous cruise conference at the start of April. For a relatively ‘small’ conference (around 300-400 people), the array of quality speakers the group manage to get is always astounding.  Martin Nash, Cary Millsap, Tim Hall, Bryn Llewellyn, Martin Bach, Jeff Smith, Doug Burns to name just a few.  I gave a (more...)

adding NOT NULL columns to an existing table … implications make me grumpy

This is DBA basics 101 in the oracle world but well also something that we grumpy DBA types forget from time to time.  We have an existing table in a schema that is populated with data.  Something like this say:


create table dbaperf.has_data ( column_one varchar2(10) not null, column_two number(10) not null);

insert into dbaperf.has_data(column_one, column_two) values('First row',13 (more...)

enq: SQ – contention

This example shows how to deal with the enq: SQ – contention wait event. It was tested on Oracle 11.2. First I created a sequence and queried the amount of time already spent on this wait event:
 
SQL> create sequence seq1
  2  /
 
Sequence created.
 
SQL> select time_waited/100
  2  from v$system_event
  3  where event = 'enq: SQ - contention'
  4  /
 
no rows selected
 
SQL>

Collaborate14 Session: Cache Buffer Chains Demystified

Thank you all for coming to my session Cache Buffer Chains Demystified at Collaborate 14, especially for sticking around for a geeky topic like this to the very end. Much appreciated.

I was not aware that I would not be allowed to use my laptop; so I couldn't show all the demos I so carefully prepared. Please download the scripts and execute them yourself.

As promised, here are the materials I used in the session

(more...)

Maximum manageable storage in VMware versions

 

Maximum manageable storage per VM by ESX version

  • 4.1: 32TB (vmdk) / 120TB (RDM)
  • 5.0: 60TB (vmdk) / 3.75PB (RDM)
  • 5.1: 60TB (vmdk) / 3.75PB (RDM)
  • 5.5: 3.63PB (vmdk) / 3.75PB (RDM)

Note that the 60TB limit for 5.0 and 5.1 requires Update 1. Without this the limit is 24TB.

Exceeding the limits on ESX < 5.5 can result (more...)

Moving away from wordpress

I am sick of this advertisement on my site.

Therefor I am about to move most of my posts to

http://sysdba.ch/index.php/postlist

 

Thanks for following my blog for so long.

Lutz Hartmann


HeartBleed and Oracle

There are a lot of people asking about Heartbleed and how it has impacted the web.
Oracle has published  MOS Note 1645479.1 that talks about all the products impacted and if and when fixes will be available.
The following blog post is also a good reference about the vulnerability.  https://blogs.oracle.com/security/entry/heartbleed_cve_2014_0160_vulnerability