Oracle 12c New Feacture

• Prior to Oracle Database 12c the maximum length for a VARCHAR2 and NVARCHAR2 was 4,000, and the maximum length of a RAW column was 2,000. Starting with Oracle Database 12c, these data types have been extended to accommodate a length of 32,767.

• Prior to Oracle Database 12c, you could not have multiple indexes defined on the exact same combination of columns in one table. This has changed in 12c. You can now have multiple indexes on the same set of columns. However, you can only do this if there is something physically different about the indexes; for example, one index is created as a B-tree index, and the second, as a bitmap index. Also, there can be only one visible index for the same combination of columns. Any other indexes created on that same set of columns must be declared invisible;
• The NVARCHAR2 and NCHAR data types are useful if you have a database that was originally created with a single-byte,
• If you use a VARCHAR2 for a field that contains date information, you are guaranteeing future reporting inconsistencies and needless conversion function(such as TO_DATE and TO_CHAR).
fixed-width character set, but sometime later you need to store multibyte character set data in the same database.
• The RAW data type allows you to store binary data in a column. This type of data is sometimes used for storing globallyunique identifiers or small amounts of encrypted data. If you need to store large amounts (over 2000 bytes) of binary data then use a BLOB instead.
• You can also instruct Oracle to not re-adjust the high-water mark when shrinking a table. This is done via theCOMPACT clause—for example:
• SQL> alter table emp shrink space compact;

Oracle Pre-Installation Requisites

 ::::: Oracle Preinstallation requirements :::::::

1. create directory for oracle user home location.

( mkdir -p /u/oracle/home)

2. create group oinstall 
  groupadd -g 501 oinstall
groupadd -g 502 dba

3. create user 
 
useradd -u 503 -g oinstall -G dba -d /u/oracle/home -m oracle

4. change ownership for oracle home location 

chown -R oracle:oinstall /u/oracle/home

change permission for oracle home location

chmod -R 775 /u/oracle/home

5. create direcrory for oracle binary location 

mkdir -p /u/oracle/server

6. change ownership for oracle home location 

chown -R oracle:oinstall /u/oracle/server
   change permission for oracle home locatio 
chmod -R 775 /u/oracle/server

7. install required packages for oracle 

binutils-2.17.50.0.6-2.el5
compat-libstdc++-33-3.2.3-61
elfutils-libelf-0.125-3.el5
elfutils-libelf-devel-0.125
glibc-2.5-12
glibc-common-2.5-12
glibc-devel-2.5-12
glibc-headers-2.5-12
gcc-4.1.1-52
gcc-c++-4.1.1-52
libaio-0.3.106
libaio-devel-0.3.106 
libgcc-4.1.1-52
libstdc++-4.1.1 
libstdc++-devel-4.1.1-52.e15
make-3.81-1.1
numactl-devel-0.9.8.i386
sysstat-7.0.0

unixODBC-2.2.11 (32 bit) or later
unixODBC-devel-2.2.11 (32 bit) or later

8. change kernel parameter

vi /etc/sysctl.conf

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

run (/sbin/sysctl.conf -p) to refect in current session


9. change ulimit for oracle

Add the following lines in the /etc/security/limits.conf file:

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


10. copy oracle or grid infrastucture  binary to guest system. change ownership and permission to oracle

*** run on root user  #Xhost +

11. Use grid infrastructure or oracle for standlone server or cluster servers

*** run on oracle user $./runInstaller

    Use password for asm (if Grid installation ) for Sys pass (if Oracle installation) 

oracle base : /u/oracle/server
     oracle home : /u/oracle/gri203 or database203
     oracle inventory : /u/oracle/server/oraInventory

12. complete installation 

13. Run post installation scripts on root and oracle user as per the instruction will find while installation.