What are Patches and how to apply patches ?

Patching  is one  of  the  most  common  task  performed  by  DBA's  in  day-to-day  life  . Here , we  will discuss  about  the various  types  of  patches  which  are  provided  by  Oracle  . Oracle  issues  product fixes  for  its  software called  patches. When  we  apply  the  patch  to  our  Oracle  software installation, it updates  the  executable  files, libraries,  and  object  files in  the software  home directory . The patch application  can  also  update  configuration  files and  Oracle-supplied  SQL schemas . Patches  are  applied by  using  OPatch, a utility supplied by Oracle , OUI  or  Enterprise Manager Grid Control . 

Oracle Patches are of various kinds . Here , we are broadly categorizing  it  into  two groups .

1.) Patchset  : 
2.) Patchset Updates : 

1.) Patchset  :  A group of  patches  form  a  patch  set. Patchsets  are  applied  by  invoking OUI (Oracle Universal Installer) . Patchsets  are  generally  applied  for  Upgradation  purpose . This  results  in  a version change  for our  Oracle  software, for  example,  from  Oracle Database 11.2.0.1.0  to  Oracle  Database 11.2.0.3.0.  We will cover this issue later .

2.) Patchset Updates : Patch Set Updates  are  proactive cumulative patches containing  recommended bug fixes that are released on a regular and predictable schedule .  Oracle has catergaries as :

i.) Critical Patch Update (CPU)  now refers  to  the  overall  release of security  fixes each  quarter  rather than the cumulative database security  patch  for  the quarter.  Think  of  the  CPU as  the  overarching quarterly release and not as a single patch .

ii.) Patch Set Updates (PSU)  are  the same cumulative patches  that  include  both  the  security  fixes and priority  fixes.  The key with  PSUs  is  they are  minor version  upgrades   (e.g., 11.2.0.1.1  to  11.2.0.1.2). Once a  PSU  is  applied, only  PSUs  can  be  applied  in  future  quarters  until  the database  is  upgraded to a new base version. 

iii.) Security Patch Update (SPU)  terminology  is  introduced  in  the October 2012 Critical Patch Update as  the  term  for the quarterly security patch.  SPU  patches are the same  as  previous  CPU  patches,  just a new  name .  For  the database, SPUs  can  not  be  applied  once  PSUs  have  been  applied  until  the database is  upgraded  to a  new base version.

iv.) Bundle Patches  are the quarterly patches for Windows  and  Exadata  which  include  both the quarterly security patches as well as recommended fixes. 

PSUs(PatchSet Updates) or CPUs(Critical Patch Updates) ,SPU are applied via opatch utility.

How to get Oracle Patches :

We  obtain  patches  and  patch  sets  from  My Oracle Support (MOS) . The  ability  to  download a specific  patch  is  based  on  the contracts associated  to  the support  identifiers  in  our  My Oracle Support  account.  All  MOS  users  are  able  to  search  for  and  view all  patches,  but  we  will  be prevented  from  downloading  certain types  of  patches  based  on  our  contracts.

While   applying   Patchset or  patchset upgrades , basically there are two entities in the Oracle Database environment 

i. )  Oracle Database Software
ii.)  Oracle Database

Most of the database patching activities involve, in the following sequence

•  Update  "Oracle Database Software"  using   './runInstaller'  or   'opatch apply'   known  as "Installation"  Tasks.
• Update  "Oracle Database"  (catupgrd.sql  or  catbundle.sql ...etc)  to  make  it  compatible  for  newly  patched  "Oracle database Software"   known  as  "Post Installation"  tasks. 

Patchset  OR  CPU/PSU  (or one-off)  patch  contains  Post  Installation  tasks  to  be  executed  on  all Oracle  Database  instances  after  completing  the Installation  tasks. If  we  are  planning  to  apply  a patchset  along  with  required  one-off-patches (either CPU or PSU or any other one-off patch),  then  we can  complete  the  Installation  tasks  of  the   Patchset+CPU/PSU/one-off  patches at once and then execute  Post  Installation  tasks of  the  Patchset+CPU/PSU/one-off  patches  in  the  same sequence as they were  installed . 

This  approach  minimizes  the  requirement  of  database  shutdown  across  each  patching  activity and simplifies  the  patching  mechanism as two tasks: 

• Software update and then
• Database update.

Here , we  will  cover  the  Opatch Utility in details along with example. 

OPatch  is  the  recommended (Oracle-supplied)  tool  that  customers  are  supposed  to  use  in  order to apply  or  rollback  patches. OPatch  is  PLATFORM  specific . Release is based on Oracle Universal Installer version .   OPatch  resides in  $ORACLE_HOME/OPatch .  OPatch  supports  the  following :

• Applying  an  interim  patch.
• Rolling  back  the  application  of  an  interim  patch.
• Detecting  conflict  when  applying  an  interim  patch  after  previous  interim  patches  have  been applied.  It  also  suggests  the  best  options  to  resolve a conflict .
• Reporting on installed products and interim patch.

The  patch  metadata  exist in  the  inventory.xml  and  action.xml  files  exists under <stage_area>/<patch_id>/etc/config/   

Inventory  .xml  file  have  the  following  information :

• Bug number 
• Unique Patch ID
• Date of  patch year  
• Required and Optional components 
• OS platforms ID 
• Instance shutdown is required or not 
• Patch can be applied online or not 

Actions   .xml  file  have  the  following  information .

• File name and it location to which it need to be copied 
• Components need to be re-linked 
• Information about the optional and required components

Here are steps for applying  patches on linux Platform : 

1.) Download the required Patches from  My Oracle Support (MOS) : 

• Login to metalink.
• Click "Patches & Updates" link on top menu.
• On the patch search section enter patch number and select the platform of your database.
• Click search.
• On the search results page, download the zip file.

2.)  Opatch version  :
Oracle  recommends  that  we  use  the  latest  released  OPatch , which  is  available  for  download  from My  Oracle  Support .  OPatch  is compatible  only  with  the version  of  Oracle  Universal  Installer  that  is installed  in  the  Oracle  home. We  can  get  all  Opatch  command  by  using  Opatch  help  command .

3.) Stop all the Oracle services  :
Before applying Optach , make sure all the Oracle services are down . If they are not down then stop/down the oracle related Services . Let's crosscheck it 

$ ps -ef |grep pmon
oracle   15871 15484  0 11:20 pts/2    00:00:00 grep pmon

$ ps -ef |grep tns
oracle   15874 15484  0 11:20 pts/2    00:00:00 grep tns

4.) Take Cold Backup :  

It  is  highly  recommended  to backup  the software  directory  which  we  are  patching  before  performing any  patch  operation . This  applies  to  Oracle  Database  or Oracle  Grid  Infrastructure  software installation  directories.  Take the backup of following 

• Take the Oracle software directory backup 

$ tar -zcvf   /u01/app/oracle/product/11.2.0/ohsw-bkp-b4-ptch.tar.gz   /u01/app/oracle/product/11.2.0   

• Take  backup of oracle database . 

$ tar  -zcvf    /u01/app/oracle/oradata/dbfl-b4-ptch.tar.gz     /u01/app/oracle/oradata     
Here all the database files are in oradata  directory .

• Take backup of OraInventary

$ tar  -zcvf   /u01/app/oraInventary/orinv-b4-ptch.tar.gz     /u01/app/oraInventary  


5.)  Apply  OPatches 
Set  our current directory to the directory where the patch is located and then run the OPatch utility by entering the following commands:

$ export  PATH=$ORACLE_HOME/OPatch:$PATH:
$ opatch apply .

6.)  Post Installation : 

Once , the  Opatch  installation  completed  successfully . Perform  the  post  Installation steps . Startup  the oracle  database  with  new  patched  software and  run catbundle.sql  scripts  which  is  found  in           $ORACLE_HOME/rdbms/admin   directory .

The catbundle.sql execution is reflected in the dba_registry_history view by a row associated with bundle series PSU.


7.) Finally check the status of patch status : 
We can check the final status of applied patched new Oracle Home by using the below command .
SQL > select  *   from  dba_registry_history   order  by  action_time  desc ;


Notes :
i.) If  we are using  a  Data Guard Physical Standby database, we  must  install  this  patch  on  both  the primary  database and  the physical  standby database .

ii.)  While applying patching take care of  mount point status .There should be sufficient Space .


There are few good demo on Optach . Check the below link 
Click Here
Click Here

For More About Opatch : Click Here


Enjoy   :-)   :-)