The script for the demonstration from the tutorial can be downloaded here:seg_demo

Until 11gR2, if you create a table, Oracle database allocates space for initial segment.

The new feature allows you to defer creation of this initial segment until the first row of data is inserted into the table.

In addition to deferring the table’s segment, it also defers the segment creation for LOB columns of the table, indexes created implicitly as part of table creation, and indexes subsequently explicitly created on the table.

By using this feature, large amount of disk space can be saved in case of many unpopulated tables.

A new parameter DEFERRED_SEGMENT_CREATION is created to control the feature. It can be enabled/disabled it at the session or system level (doesn’t require Instance restart).

Alter session set deferred_segment_creation=true;

Alter system set deferred_segment_creation=true;
  

Deferred segment creation is enabled by default. It’s also possible to enable/disable it for a single table by specifying the deferred segment creation clause.

CREATE TABLE.... SEGMENT CREATION IMMEDIATE

CREATE TABLE... SEGMENT CREATION DEFERRED
 

* A table with deferred segment won’t exist in the *_EXTENTS System view before inserting into it data (as no extent is created)
* A new column was added to the *_TABLES,  *_INDEXES and *_LOBS System views – SEGMENT_CREATED, whichindicates whether the initial segment was created or not. Its values are ‘YES’ / ’NO’.

One important note – All segments related to a table are created when the first row is inserted into it. And that, even if they are not used to store data

Following is a short demo that demonstrates the new features.

SQL> @c:\seg_demo
====================================================================
Creating a user for the demonstration and granting it privileges:
====================================================================

SQL> CREATE USER seg_demo identified by seg_demo
User created.
SQL> GRANT RESOURCE , CONNECT TO seg_demo
Grant succeeded.
SQL> GRANT SELECT ON V_$PARAMETER TO seg_demo
Grant succeeded.
SQL> CONNECT seg_demo/seg_demo
Connected.

====================================================================
Displaying relevant parameters
====================================================================

SQL> SHOW PARAMETER def
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
deferred_segment_creation            boolean     TRUE
SQL> SHOW PARAMETER compatible
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
compatible                           string      11.2.0.0.0

=========================================================================================
Creating a table. The table will be created without segments for all its related objects
=========================================================================================

SQL> CREATE TABLE test_seg (id number CONSTRAINT id_pk primary key,
2				email VARCHAR2(50)  CONSTRAINT  email_uk unique,
3				name VARCHAR2(30),
4				data CLOB)
5			lob(data) STORE AS TEST_SEG_DATA_LOB
6			(index test_seg_data_lob_ix)
Table created.

=========================================================================================
Displaying relevant information FROM the System views.
=========================================================================================

SQL> SELECT segment_name ,SEGMENT_TYPE
2	FROM user_segments
3 	WHERE segment_name = 'TEST_SEG'

no rows selected

SQL> SELECT segment_name, extent_id, bytes
2 	FROM user_extents

no rows selected

SQL> SELECT table_name, SEGMENT_CREATED
2 	FROM user_tables

TABLE_NAME                     SEGMENT_CREATED
------------------------------ ---------------
TEST_SEG                       NO

SQL> SELECT table_name, index_name, SEGMENT_CREATED
2 	FROM user_indexes

TABLE_NAME                     INDEX_NAME                     SEGMENT_CREATED
------------------------------ ------------------------------ ---------------
TEST_SEG                       ID_PK                          NO
TEST_SEG                       TEST_SEG_DATA_LOB_IX           NO
TEST_SEG                       EMAIL_UK                       NO

SQL> SELECT  TABLE_NAME ,segment_name, SEGMENT_CREATED
2 	FROM user_lobs

TABLE_NAME                     SEGMENT_NAME         SEGMENT_CREATED
------------------------------ -------------------- ---------------
TEST_SEG                       TEST_SEG_DATA_LOB    NO

=========================================================================================
Inserting the first row to the table.
=========================================================================================

SQL> INSERT INTO TEST_SEG VALUES (1,'Roni@@dbsnaps.com','DBSNAPS','Deferred Segment Creation')

1 row created.

SQL> commit

Commit complete.

=========================================================================================
All the relevant segments will be created.
Displaying relevant information FROM the System views.
=========================================================================================

SQL> SELECT segment_name ,SEGMENT_TYPE
2 FROM user_segments

SEGMENT_NAME         SEGMENT_TYPE
-------------------- ------------------
TEST_SEG             TABLE
TEST_SEG_DATA_LOB_IX LOBINDEX
ID_PK                INDEX
EMAIL_UK             INDEX
TEST_SEG_DATA_LOB    LOBSEGMENT

SQL> SELECT segment_name, extent_id, bytes
2 	FROM user_extents

SEGMENT_NAME          EXTENT_ID      BYTES
-------------------- ---------- ----------
TEST_SEG                      0      65536
TEST_SEG_DATA_LOB_IX          0      65536
ID_PK                         0      65536
EMAIL_UK                      0      65536
TEST_SEG_DATA_LOB             0      65536
SQL> SELECT table_name, SEGMENT_CREATED
2 	FROM user_tables

TABLE_NAME                     SEGMENT_CREATED
------------------------------ ---------------
TEST_SEG                       YES

SQL> SELECT table_name, index_name, SEGMENT_CREATED
2 	FROM user_indexes
TABLE_NAME                     INDEX_NAME                     SEGMENT_CREATED
------------------------------ ------------------------------ ---------------
TEST_SEG                       ID_PK                          YES
TEST_SEG                       TEST_SEG_DATA_LOB_IX           YES
TEST_SEG                       EMAIL_UK                       YES
SQL> SELECT  TABLE_NAME ,segment_name, SEGMENT_CREATED
2 	FROM user_lobs

TABLE_NAME                     SEGMENT_NAME         SEGMENT_CREATED
------------------------------ -------------------- ---------------
TEST_SEG                       TEST_SEG_DATA_LOB    YES

=========================================================================================
The parameter can be changed in the System/Session level.
Changing the session settings to deferred_segment_creation=FALSE.
=========================================================================================

ALTER SESSION SET deferred_segment_creation=FALSE

Session altered.

=========================================================================================
While this parameter is set to FALSE, tables will be created with all their segments.
=========================================================================================
prompt
SQL> CREATE TABLE test_seg2 (id number CONSTRAINT id2_pk primary key,
2    			name VARCHAR2(30))

Table created.

=========================================================================================
Displaying relevant information FROM the System views.
=========================================================================================

SQL> SELECT segment_name ,SEGMENT_TYPE
2 	FROM user_segments
3 	WHERE segment_name = 'TEST_SEG2'

SEGMENT_NAME         SEGMENT_TYPE
-------------------- ------------------
TEST_SEG2            TABLE
SQL> SELECT segment_name, extent_id, bytes
2 	FROM user_extents
3 	WHERE segment_name = 'TEST_SEG2'

SEGMENT_NAME          EXTENT_ID      BYTES
-------------------- ---------- ----------
TEST_SEG2                     0      65536

SQL> SELECT table_name, SEGMENT_CREATED
2 	FROM user_tables
3 	WHERE table_name = 'TEST_SEG2'

TABLE_NAME                     SEGMENT_CREATED
------------------------------ ---------------
TEST_SEG2                      YES

SQL> SELECT table_name, index_name, SEGMENT_CREATED
2 	FROM user_indexes
3 	WHERE table_name = 'TEST_SEG2'

TABLE_NAME                     INDEX_NAME                     SEGMENT_CREATED
------------------------------ ------------------------------ ---------------
TEST_SEG2                      ID2_PK                         YES

=========================================================================================
In addition, the feature can be enabled/Disabled for a Single table.
While the parameter is set to TRUE, we will disable the deferred segment creation for a single table .
=========================================================================================

ALTER SESSION SET deferred_segment_creation=TRUE

Session altered.

SQL> CREATE TABLE test_seg3 (id number CONSTRAINT id3_pk primary key,
2	    			name VARCHAR2(30))
3				SEGMENT CREATION IMMEDIATE

Table created.

=========================================================================================
Displaying relevant information FROM the System views.
=========================================================================================

SQL> SELECT segment_name ,SEGMENT_TYPE
2 	FROM user_segments
3 	WHERE segment_name = 'TEST_SEG3'

SEGMENT_NAME         SEGMENT_TYPE
-------------------- ------------------
TEST_SEG3            TABLE

SQL> SELECT segment_name, extent_id, bytes
2 	FROM user_extents
3	WHERE segment_name = 'TEST_SEG3'

SEGMENT_NAME          EXTENT_ID      BYTES
-------------------- ---------- ----------
TEST_SEG3                     0      65536

SQL> SELECT table_name, SEGMENT_CREATED
2 	FROM user_tables
3 	WHERE table_name = 'TEST_SEG3'

TABLE_NAME                     SEGMENT_CREATED
------------------------------ ---------------
TEST_SEG3                      YES

SQL> SELECT table_name, index_name, SEGMENT_CREATED
2 	FROM user_indexes
3 	WHERE table_name = 'TEST_SEG3'

TABLE_NAME                     INDEX_NAME                     SEGMENT_CREATED
------------------------------ ------------------------------ ---------------
TEST_SEG3                      ID3_PK                         YES

=========================================================================================
While the parameter is set to FALSE, we will Enable the deferred segment creation for a single table .
=========================================================================================

SQL> ALTER SESSION SET deferred_segment_creation=FALSE

Session altered.

SQL> CREATE TABLE test_seg4 (id number CONSTRAINT id4_pk primary key,
2         			name VARCHAR2(30))
3  	SEGMENT CREATION DEFERRED

Table created.

=========================================================================================
Displaying relevant information FROM the System views.
=========================================================================================

SQL> SELECT segment_name ,SEGMENT_TYPE
2	FROM user_segments
3 	WHERE segment_name = 'TEST_SEG4'

no rows selected

SQL> SELECT segment_name, extent_id, bytes
2 	FROM user_extents
3 	WHERE segment_name = 'TEST_SEG4'

no rows selected

SQL> SELECT table_name, SEGMENT_CREATED
2 FROM user_tables
3 WHERE table_name = 'TEST_SEG4'

TABLE_NAME                     SEGMENT_CREATED
------------------------------ ---------------
TEST_SEG4                      NO

SQL> SELECT table_name, index_name, SEGMENT_CREATED
2 	FROM user_indexes
3 	WHERE table_name = 'TEST_SEG4'

TABLE_NAME                     INDEX_NAME                     SEGMENT_CREATED
------------------------------ ------------------------------ ---------------
TEST_SEG4                      ID4_PK                         NO

=========================================================================================
The END. Dropping the demonstration user
=========================================================================================

SQL> CONNECT / as sysdba

Connected.

DROP USER seg_demo CASCADE

User dropped.

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• Address regulatory requirements—Implement separation-of-duty and other real-time preventive controls.
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Then came Oracle 11g with the “active standby database” feature (sometimes referenced as real-time query).

With this feature we can open the database in “read only” mode, and can still apply archive logs from the primary.

Let’s see how it works…

When installing Oracle on Linux, there are several prerequisites steps that needs to be completed before the installation process ifself.
The installation GUI is identical to other operating systems, but the steps we need to complete before starting the installation are different.
This video will show you how to install Oracle 11gR1, step by step.

This video shows Oracle 11gR1 installation on Linux Cent OS 5 (which is similar to RedHat 5), but can be used to understand the general Oracle installation on Linux.

You can download the Oracle Database software from OTN:

• Oracle Database 11g Release 1- OTN

We will start by checking the requirements for Oracle installation.

1)    Checking the memory, SWAP, Kernel version and free space requirements.

Memory – Oracle 11g requires at least 1GB RAM.
You’ll be able to check the server’s memory by executing the command:

[root ~]grep MemTotal /proc/meminfo

Swap requirements are specified in the documentation and based on the RAM.
Check the server’s SWAP by executing the command:

[root ~]grep SwapTotal /proc/meminfo

At least 400Mb are needed in /tmp directory. In addition, Oracle 11g software requires about 3.5GB.
Check the /tmp available space by executing the command:

[root ~]df -k /tmp

Check the server’s available space by executing the command:

[root ~]df -k

The available column will display the free space in kilobytes.

The OS kernel version should be 2.6.18 or higher.
Check the kernel version by executing the command:

[root ~] cat /proc/version
OR
[root ~] uname –r

2)     Required Packages

Oracle 11g software needs several rpm packages to be installed on the server.
You can find the full list of packages in the installation guide:
http://download.oracle.com/docs/cd/B28359_01/install.111/b32002/pre_install.htm#CHDHFGBJ

The command “rpm -qa” prints the list of all installed packages. With “grep” command we will look for specific packages.

Example: to verify that the gcc package is install, use:

[root ~]rpm –qa | grep gcc

3)    Creating users and groups.

We will create two new groups: ‘dba’ and ‘oinstall’ and the ‘oracle’ user.

[root ~] groupadd oinstall
[root ~] groupadd dba
[root ~] useradd -g oinstall -G dba oracle
[root ~] passwd oracle

4)    Setting Kernel parameters.

Open the /etc/sysctl.conf file  and configure the following kernel parameters:

fs.file-max = 6815744
kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
net.ipv4.ip_local_port_range = 9000 65500
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048576

Additional information about the kernel parameter can be found in the Documentation:
http://download.oracle.com/docs/cd/B28359_01/install.111/b32002/pre_install.htm#BABBBDGA

After editing the file, execute the following command to apply the changes.

[root ~] sysctl -p

5)     Add the following lines to the /etc/security/limits.conf file:

oracle              soft    nproc    2047
oracle              hard    nproc   16384
oracle              soft    nofile  1024
oracle              hard    nofile  65536

6)    Add the following line to the /etc/pam.d/login file:

session   required   pam_limits.so

7)    Add the following lines to the /etc/profile file: This section sets the soft limit for user ‘oracle’ upon login:

if [ $USER = "oracle" ]; then
 if [ $SHELL="/bin/ksh" ] ; then
    ulimit -p 16384
    ulimit -n 65536
 else
    ulimit -p 16384 -n 65536
 fi
fi

8)    Creating directories for the Oracle installation: We need to create the directory for Oracle installation. This directory should be owned by user ‘oracle’

[root ~]mkdir -p /u01/app/oracle/product/11.1.0/db_1
[root ~]chown -R oracle:oinstall /u01
[root ~]chmod -R 775 /u01

9)    Disable access control:

Access control does not allow opening X-Windows from any server. We will use xhost command to disable this access control.

[root ~] xhost +

10)   Edit the /etc/profile file:

We will now connect as user ‘oracle’ and configure the environment in the bash_profile file.

[root ~]su – oracle
[oracle ~]vi .bash_profile

We will set the ORACLE_BASE for oracle base directory and ORACLE_SID environment variables. Add the following lines to bash_profile file:

export ORACLE_HOSTNAME=<SERVER_NAME>
export ORACLE_BASE=/u01/app/oracle;
export ORACLE_HOME=$ORACLE_BASE/product/11.1.0/db_1;
export ORACLE_SID=orcl;

Apply the changes so that the new variables will be set:

[oracle ~] . .bash_profile

The pre-requirement part is completed. All we have to do now is to start the installation.

11)    Navigate to the installation directory and start the installation:

[oracle ~] cd /install/database
[oracle ~] ./runInstaller

We will skip the installation part as it is quite straightforward, and go to the end of the installation part.

12)    Execute configuration scripts as root user:

At the end of the installation, you’ll see the “execute configuration scripts” wizard window. We should run these scripts as root. Open a Terminal as root and execute the below scripts”

[root ~] /u01/app/oracle/oraInventory/orainstRoot.sh
[root ~] /u01/app/oracle/product/11.1.0/db_1/root.sh

The installation is now complete.

13)    Updating the .bash_profile file with more environment variables:

The last thing we need to do is updating the .bash_profile file:

[oracle ~] vi .bash_profile

We will set the ORACLE_HOME for oracle home directory and the path environment variables. Add the following lines to bash_profile file:

export ORACLE_HOSTNAME=<SERVER_NAME>
export ORACLE_BASE=/u01/app/oracle;
export ORACLE_HOME=/u01/app/oracle/product/11.1.0/db_1;
export ORACLE_SID=orcl;
export PATH=/usr/sbin:$PATH;
export PATH=$PATH:$HOME/bin:$ORACLE_HOME/bin

Apply the changes so that the new variables will be set:

[oracle ~]. .bash_profile

14) Verify that everything is configured correctly.

[oracle ~] sqlplus / as sysdba

SQL*Plus: Release 11.1.0.1.0 Production on Mon Oct 25 12:26:26 2010

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

Connected to:

Oracle Database 11g Enterprise Edition Release 11.1.0.1.0 - 64bit Production

With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL>exit

Transaction log files are copied from the production SQL server, and then restoring them onto a standby server. But this is not all. The key feature of log shipping is that is will automatically backup transaction logs throughout the day (for whatever interval you specify) and automatically restore them on the standby server. This in effect keeps the two SQL Servers in “synch”. Should the production server fail, all you have to do is point the users to the new server, and you are all set. Well, its not really that easy, but it comes close if you put enough effort into your log shipping setup.

Watch this video tutorial and see how you can benefit from Oracle Enterprise Single Sign-On.