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What data type should I use: CHAR or VARCHAR2???

Hi,

We all know that CHAR and VARCHAR2 are two different datatypes used for storing strings in Oracle. When I asked many people about what’s the difference exactly, all were saying VARCHAR2 can be used for variable sized character strings. As I’m not satesfied with the answer, as always, I’ve decided to do my own experiments on these two. Please find the exercise I’ve performed below.

SQL> create table t1 (col1 char(10), col2 varchar2(10));

Table created.

SQL> insert into t1 values(‘Oracle’,'Oracle’);

1 row created.

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“ORA-01081: cannot start already-running ORACLE” While creating a new Database

Hi Geeks,

When I was doing a research on Oracle Database creation, through DBCA, last week, I came across a very interesting scenario which I couldn’t stop sharing with you :)

I have a cluster of machines (don’t confuse it with a RAC cluster but just a group of machines required for my application deployment) with 11.2.0.2 installed and a Database instance running.

I got a requirement to remove everything accumulated in the machine as a result of the Oracle installation and the Database creation: The installation directories, the datafiles, oratab entries etc…

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Can you create objects in a READ ONLY tablespace?

Hi Oracle geeks,

Last Friday, I’ve noticed a strange thing happening in my 11.2.0.3 Database: I’m able to create objects in a tablespace which is marked READ ONLY !!!

Don’t believe this?? See the below

SQL> create tablespace ro datafile ‘/xxx/RO.DBF’ size 10M AUTOEXTEND ON;
Tablespace created.

SQL> alter tablespace ro read only;
Tablespace altered.

SQL> select status from dba_tablespaces where tablespace_name=’RO’;
STATUS
———
READ ONLY

SQL> sho user
USER is “CSM“

Key Value Pair Data Model

I have just joined an in flight project and find the lead data modeler has created a name value pair data model.

The reason given was flexibility of data model considering some records can have as many as 900 attributes. The .Net application team seem to be loving it, as they can code everything with very few tables in mind.

I feel the model is difficult to query, difficult to load and difficult to syndicate and in all likelyhood will suffer from poor performance. Also the data model can't be considered as a rich metadata repository and difficult to understand.

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Tools to Administer, Monitor and Tune the Oracle Database.

I just posted a complete integrated set of tools to manage, monitor and tune the Oracle database.

It is free, no registration or email is required. I will just appreciate any kind of feedback to make it better.

The package comprises the following topics:

Objects
This section allows you to view and maintain virtually all database objects, including partitioned tables and materialized views. It also includes a function to view inter-dependency between objects.

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1Z0-052 Oracle DBA Admin 1 OCA Study Guide by Matthew Morris: Review

Matthew Morris (who makes many constructive and knowledgeable contributions to the forum) has written a series of study guides for the OCA/OCP exams. I asked him if I could have a copy of one to review. The result: it's very good. This is a copy of the review I put up on Amazon.

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How to move a table from one schema to another

The other day, I was asked how to move a table from one schema to another. The answer, as we all know, is "you can't do that: you have to create a new table as a copy of the old one, or use export/import. It will take a long long time." Not true.

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andy huang's picture

How to use Incarnation in Oracle 10G

OS:Red Hat Linux As 5
DB Version:10.2.0.4

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