Category Archives: Oracle

10 Features in Oracle 12c for Developers

Last updated on November 26th, 2014 at 07:07 am

Dear All,
After a long break and holiday season, today I tried my hands on some new features in Oracle 12c for developers.
There has been flood of articles, blog posts, seminars, webinars, conference presentations, videos on Oracle 12c since its launch, which is making wave in the cyber world. Over the years I have learnt to overcome this overwhelming phenomenon in my own way.  The idea is to create my own list of favorite features in new release of Oracle Database and post it 🙂

But all that remained enigma until I tried some of the features today. I have narrowed down my list to 10 features for developers in Oracle 12c.


Source: ToadWorld – Oracle 12c understanding the version number

Did you know that Oracle release version number says a lot about the Oracle Database Product you are working on? There is a one article on understanding Oracle version numbers by Dan Hotka. In case you are interested you can access it on ToadWorld website here.

The presentation content for my Top 10 Features in Oracle 12c for Developers can be found here.

You can download the – setup script and demo script available on my website.

I would like to end this post by sharing a wonderful interactive guide on Oracle 12c. The interactive guide is available on Oracle website here.

Hope you find the content useful and it gives you head start to latest release of Oracle 12c.

Vijay Mahawar

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Posted by on February 1, 2014 in DBA, Oracle, PL/SQL


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Top 12 Features of Oracle Database 12c

Last updated on November 26th, 2014 at 07:07 am

Source: Oracle on Youtube
With over 500 new features – narrowing down to a few favorites was a daunting task.
But Tom Kyte, Vice President of Oracle, (of AskTom fame) was up to the challenge and shares his top 12 features of Oracle Database 12c.

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Posted by on November 13, 2013 in DBA, Oracle, PL/SQL


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Now I am OCE in Oracle RAC 11g and Grid Infrastructure Administrator

Last updated on November 26th, 2014 at 07:07 am

Oracle OCE RAC 11g and GridIt gives me immense pleasure to inform you that now I am Oracle Certified Expert in Oracle Real Application Clusters 11g R2 and Grid Infrastructure Administrator.

Today, I passed the exam 1Z0-058. The exam comprised of two sections:

Section 1: Grid Infrastructure: Clusterware and ASM and
Section 2: Real Application Clusters

I secured 79% in section 1 and 73% in section 2.

I thank all my friends who encouraged me and supported me to achieve this feat.


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Posted by on September 24, 2013 in DBA, Oracle


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Steps for Installing RAC with ASM on Oracle Database 12c

Last updated on January 17th, 2016 at 06:56 am

Hi Friends,

In  continuation to my previous posts on Workshop on RAC and ASM and 12c New Feature Pluggable Database. Today I am posting the installation steps for RAC with ASM on the latest Oracle Database 12c release, which I managed to install on my laptop.

Disclaimer: Please consider this as only checklist and steps and not a end-to-end installation guide to install RAC with ASM on Oracle Database 12c.

Following is the list of steps which I had performed for my installation:

1. Download Oracle VM VirtualBox from here.
2. Download Oracle Enterprise Linux 6 from Edelivery



3. Download Oracle 12c Database for Linux 64 bit (2 Parts – size ) from Edelivery (highlighted in above image)
4. Download Oracle 12c Database Grid for Linux 64 bit (2 Parts – size ) from Edelivery (highlighted in above image)
5. Install VM Virtual Box and OEL 6 on VM Virtual Box.
VirtualBox Guest Additions Package can be installed from this location. Post installation it will prompt you to install the extension package which can be downloaded from here.
6. OEL6 comes with pre-installed oracle users and oinstall users. Ensure that you select the package oracle-rdbms-server-11gR2-preinstall available under system tools. More information on this is available here.
7. At this point, its better if you take the snapshot of your virtual machine. This would help you to avoid repeating the previous steps incase of any issues.
8. Setup the .bash_profile, grid_env and db_env in oracle user home directory.
9. Setup the public ip address, vip address, private address and scan address in the /etc/hosts file.
10. Create directory for oracle database and inventory.
11. Copy the Oracle Software and Grid Software to the path you had mentioned in the .bash_profile.
12. Go to the Grid/rpm directory and install rpm cvuqdisk-1.0.9-1.rpm.
13. Create ASM disks and make it shareable. Login as root  partition the disks created under /dev using fdisk command.
14. Install oracleasmlib-2.0.4-1.el6.x86_64.rpm. Use the oracleasm command to createdisks for asm using the disks created in step 12.
15. Clone the Virtual Machine for second node. Ensure that firewall on both the machine are disabled.
16. Configure the second node for Network (for public address and vip address)
17. Setup the SSH password less connectivity to avoid the user equivalence error.
18. Copy the Oracle 12c database files in the inventory location (under /u01)
19. Install the Grid (from /u01/grid/runInstall)
20. This will invoke Installer for Oracle Grid Infrastructure. The wizard includes 13 steps. Including mainly cluster configuration and Creation of ASM Disk Groups.
21. Now, the system is ready to install the Oracle 12c Database (goto /u01/database and run ./runInstaller)
22. At this point, its better if you take the snapshot of your virtual machine again. This would help you to avoid repeating the previous steps in case of any issues.
23. The above command will launch the Oracle Database 12c Release 1 Installer, which is again a 13 steps.
24. Login into the sqlplus and confirm the installation. As shown in below screenshot:

Some Errors which I came across while installing RAC with ASM:

1. OEL6 by default gets installed without desktop and GUI. Default package installation of OEL6 does not include desktop GUI installation. This was resolved by clicking on custom option and selecting the desktop view. (You can also choose either gnome or kde)
2. User Equivalence Error.  This was resolved by setting the SSH connectivity and disabling the firewall.
3. Network ethernet settings post clone were not set up properly this led to error while setting up the cluster settings at the time of GRID installation.
4. I missed out step to install cvuqdisk-1.0.9-1.rpm.
5. ASM location was not showing during the GRID installation. This was due to the missing oracleasm rpm.
6. First installation failed because of shortage of disk space. Only 25GB of disk space which was allocated. This was resolved by allocating 35GB to the virtual disk. In addition to this I had allocated 5GB to each ASM disks. Making the total space for the installation for 1 rac node 50GB and if I include the clone node the total installation used up 85GB. Since ASM disks were shared between the nodes.
7. During the Database installation. Database was showing as ‘orcl.localdomain’ by default. This had to be changed to RAC as configured in the .bash_profile file.

Hope you find this steps and content useful for installing RAC on Oracle 12c with ASM. Please feel free to leave your comments.

Happy ‘RAC’ ing 🙂

Visit Vijay’s Oracle photo gallery here and know more about him here

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Posted by on August 28, 2013 in DBA, Oracle


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Oracle Database 12c: New Feature – Pluggable Databases

Last updated on November 26th, 2014 at 07:07 am

The much anticipated 12c version of Database was made available for download on 25th June 2013 on OTN here. The most important new feature in this latest release is the Pluggable Databases.

This will give a big boost and strong hold to Oracle in the Cloud technology and rightly ‘c’ in ’12c’ stands for cloud.

I have tried to depict this new feature of Pluggable Database in 12c using below image.

Pluggable Databases in Oracle 12c

Pluggable Databases in Oracle 12c

Hope my analogy to explain all important new feature of Pluggable Database is all my readers.


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Posted by on July 7, 2013 in DBA, Oracle


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Workshop on Oracle 11gR2 DBA: RAC and ASM

Last updated on January 17th, 2016 at 07:00 am

23, 24, 25, 26 February 2013
Hotel Lemon Tree, Electronic City, Bangalore, India.

Workshop on Oracle 11gR2 DBA – RAC and ASM

Recently I had attended the workshop on Oracle RAC and ASM at Electronic City, Bangalore, India. The training was given by RAC guru Murali Vallath. I am sharing my learning and experience from this workshop.

I sincerely thank Murali for inspiring and encouraging me to learn the latest feature in Oracle – RAC and ASM.

The training batch comprised participants from different geographical location and spanning different industries. I feel lucky to be part of this batch.  Lastly, I thank Sai Ram for organizing this workshop.

TrainingBatchStanding (L to R): Syed, Abul, Chandra, Amit, Prabhakar, Vijay (me), Vasu,  Rukmini
Sitting (L to R): Bikash, Gautam, Murali, Kushal, Milind, Vivek, Sathish
Photo clicked by Sai Ram, Venue: Lemon Tree Hotel, Electronic City, Bangalore, India

What is Clustering?

Clustering is the grouping of individual computers in such a way that they can act as a single computer system. These combined resources can then be presented to applications as a single system.  One benefit of a cluster is that the application does not need to be cluster “aware”, and requires no special coding to take advantage of most cluster related services.

Oracle clustering is a shared everything architecture that involves sharing of storage by the systems of the cluster.

Oracle RAC:

Oracle RAC stands for Real Application Cluster. It was introduced by Oracle with 9i release. Latest version is 11gR2.

Oracle RAC is a cluster database with a shared cache architecture that overcomes the limitations of traditional shared-nothing and shared-disk approaches to provide highly scalable and available database solutions for all your business applications. Oracle RAC is a key component of Oracle’s private cloud architecture.

Single Instance Vs RAC Instance

As can be seen from the below diagram Oracle RAC database has more than one instance, whereas the database is single and shared across all the instances. Thus focus of RAC is on share everything concept. This ensures availability of Oracle database and also the scalability. Each RAC instance is installed on different machine (called nodes) thus scaling the computing power and maximizing availability.



Below is the architecture diagram which shows the implementation of Oracle RAC instance in real life scenario. What it additionally shows is the interconnect (hb) i.e high speed communication between the RAC instances to ensure ACID (Atomicity, Consistency, Independent and Durability).



ASM (Automatic Storage Management) Instance:


An Oracle ASM instance is a special Oracle instance that manages Oracle ASM disks.

It’s an instance for Storage Management. Both the ASM and the database instances require shared access to the disks in an ASM disk group.

ASM instances manage the metadata of the disk group and provide file layout information to the database instances. Database instances direct I/O to ASM disks without going through an ASM instance.

An ASM instance is built on the same technology as a database instance. For example, an ASM instance has a system global area (SGA) and background processes that are similar to those of a database instance. However, an ASM instance cannot mount a database and performs fewer tasks than a database instance.

Oracle Commands for RAC & ASM

I have tried to highlight the commands which are used for different instances. As the system has grown with different components, so have the commands to manage and monitor them. Below table shows the list of commands, their usage, where used (RAC/ASM) and home directory where the command is located.

Commands Usage RAC ASM Home
cluvfy Cluster Verify Utility or cvu performs system checks in integrity of all nodes, integrity of OCR, connectivity between all nodes, compare properties of one node with that of other and space availability Y Y Grid Home and Oracle Home
olsnodes The olsnodes command provides the list of nodes, local node name, vip addresses of nodes, status of nodes and type of nodes in cluster. Y Oracle CRS Home, Run as root user
crsctl Starting and stopping Oracle Clusterware resources, Enabling and disabling Oracle Clusterware daemons, Checking the health of the cluster, Managing resources that represent third-party applications. Y Y* Voting disk Grid Home
srvctl Server Control Utility to manage the Oracle RAC database. SRVCTL commands to add, remove, start, stop, modify, enable, and disable a number of components/objects, such as databases, instances, listeners, SCAN listeners, services, grid naming service (GNS), and Oracle ASM.Some SRVCTL operations for instance, database, service and nodeapps modify the configuration data stored in the Oracle Cluster Registry (OCR).  Good link which shows various options for this command is here Y Y Oracle Home,Run as oracle user
asmcmd ASMCMD is a command-line utility that you can list the content, perform searches, create and remove directories and aliases, display space utilization within Automatic Storage Management (ASM) disk groups. Orafaq link for ASMCMD is here Y Preferably separate ASM home
ocrconfig The ocrconfig command is used to manage the OCR. Ocrconfig provides the ability to import, export, add, delete, restore, overwrite, backup, repair, replace, move, upgrade, or downgrade the OCR. Same command can be used for OLR using –local option. Y Y Grid Home,Run as root user
ocrdump The ocrdump utility allows you to dump the contents of the OCR or the OLR to a file or to stdout. You can then read the resulting output for diagnostic and administration purposes. Y Y Grid Home,Run as root user
ocrcheck The ocrcheck utility is used to validate the integrity of the OCR and the OLR. Use the ocrcheck command whenever you have made any changes to your cluster (such as changing the VIP for example) Y Y Grid Home,Run as root user
oifcfg The Oracle Interface Configuration Tool is used to define and administer network interfaces such as the public and private interfaces. Y Grid Home,Run as oracle User


I have tried to consolidate all processes which are available in Single Instance, RAC Instance and ASM Instance of Oracle 11gR2 Database.




Single RAC ASM
ACFS ASM Cluster File System CSS Process Y Y
ACMS Atomic Controlfile to Memory Service (ACMS). In an Oracle RAC environment Y
ARBn ASM Rebalance Process Y
ARBx Background Process Y Y
ARCH Archiver Process Y Y
ARCHMON Archive Monitor Y Y
ASMB Automatic Storage Management Y Y Y
BMRn Automatic Block Media Recovery Slave Pool Process Y
Bnnn ASM Blocking Slave Process for GMON Y
CJQ0 Job Queue Coordinator Process Y
CKPTxx Checkpoint Y Y
CTWR Change Tracking Writer Y Y
DBRM Database Resource Manager Process Y
DBWn Database Writer Y Y
DIAG Diagnostic Capture Process Y Y
DMnn Data Pump Master Process Y
Dnnn Dispatcher Y Y
DRnn ASM Disk Resynchronization Slave Process Y
EMNC EMON Coordinator Process Y Y
Ennn EMON Slave Process Y Y
EXTPROC Callout queues Y Y
FBDA Flashback Data Archiver Process Y Y
FMON File Mapping Monitor Process Y Y
GEN0 General Task Execution Process Y Y
GMON ASM Disk Group Monitor Process Y
GTX0-j Global Transaction Process. The GTX0-j process provides transparent support for XA global transactions in a RAC environment. The database autotunes the number of these processes based on the workload of XA global transactions. Y
Innn Disk and Tape I/O Slave Process Y
Jnnn Job Queue Slave Process Y
LCK0 Instance Enqueue Process. The LCK0 process manages non-Cache Fusion resource requests such as library and row cache requests. Y
LCKn Lock Process Y Y
LGWR Log Writer Y Y
LMD Global Enqueue Service Daemon. The LMD process manages incoming remote resource requests within each instance. Y
LMHB Global Cache/Enqueue Service Heartbeat Monitor Y Y Y
LMON Global Enqueue Service Monitor. The LMON process monitors global enqueues and resources across the cluster and performs global enqueue recovery operations. Y
LMS Global Cache Service Process. The LMS process maintains records of the datafile statuses and each cached block by recording information in a Global Resource Directory (GRD). Y
MARK Mark AU for Resynchronization Coordinator Process Y Y
MMAN Background Process Y Y
MMNL Memory Monitor Light Y Y
MMON Memory Monitor Y Y
Mnnn MMON Slave Process Y Y
ORBn Background Process Y Y
OSMB Background Process Y Y
PING Interconnect Latency Measurement Process Y Y Y
PMON Process Monitor Y Y
Pnnn Parallel Query Slave Y Y
PRnn Parallel Recovery Process Y
PSP0 Process Spawner Process Y Y
QMNxx Advanced Queueing Processes Y Y
RBAL Background Process Y Y
RCBG Result Cache Background Process Y Y
RECO Distributed Transaction Recoverer Y Y
RMSn Oracle RAC Management Processes (RMSn). Y
RSMN Remote Slave Monitor manages background slave process creation and communication on remote instances. Y
RVWR Recovery Writer Y Y
Rnnn ASM Block Remap Slave Process Y
SMON System Monitor Y Y
Snnn Servers Y Y
SNPxx Snapshot process queues Y Y
VKTM Virtual Keeper of Time Process Y Y
VMB0 Volume Membership Process Y
Vnnn ASM Volume I/O Slave Process Y
Xnnn ASM Disk Expel Slave Process Y


Workshop also touched Data Guard theory and Performance Tuning in RAC.

I have tried to share what I learnt in a very simple and concise manner. I hope you find this article useful and If you feel that something could have been done better kindly drop me mail at

Vijay Mahawar

Visit Vijay’s Oracle photo gallery here and know more about him here


Posted by on March 2, 2013 in DBA, Oracle


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SPOOL APPEND – Workaround to achieve nested spool in Oracle SQL Scripts

Last updated on November 26th, 2014 at 07:07 am

Have you ever tried to execute nested scripts with spool within each file. There may have been instances when you might have had numerous sql scripts, with each having their own spool and you might have wanted to invoke them using a main script.
Like as follows:

SPOOL main.log;
.SPOOL inner1.log;
..SPOOL inner1_inner.log;


In above example you might want to have separate spool file for each of the scripts viz. main.log, inner1.log and inner1_inner.log.

But you cannot achieve this using traditional spool command prior to 10g client, where nesting of spool command was not allowed and in above scenario the main.log won’t show the result of <sql_statement_1> and <sql_statement_2>.


Starting Oracle 10g Client you can use SPOOL APPEND command which will append to the end of existing file and this can be used a workaround to achieve the nesting of spools

In the above example I can re-write the script as

SPOOL main.log;
.SPOOL inner1.log;
..SPOOL inner1_inner.log;
SPOOL main.log APPEND;

By adding the text highlighted in red you can get the output of sql_statement_1 and sql_statement_2 in main.log itself, which was missed out due to traditional nesting of spool in version of oracle client prior to 10g.

For more enhancement of SPOOL command (CREATE, REPLACE) you can visit Oracle Documentation on Spool command here.

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Posted by on February 18, 2013 in DBA, Oracle


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Understanding Performance Tuning in Oracle – Google Hangout Event

Last updated on November 26th, 2014 at 07:07 am

Dear Friends,
I will be presenting an online session on Oracle Performance Tuning. Its a Google Hangout Event to be conducted on 2nd Feb 2013, Saturday starting at 5:00 pm IST.

For details and registration please click register or click on below screenshot.

Understanding Performance in Oracle - Google Hangout Event

Looking forward to catch you all there.

For the events and session conducted by me in past you can visit the events archive section here.

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Posted by on January 26, 2013 in DBA, Oracle, PL/SQL


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UTL_MATCH – Oracle utility package to compare strings

Last updated on November 26th, 2014 at 07:07 am

Today I came across an oracle utility package to compare strings viz. UTL_MATCH. UTL_MATCH comes with Oracle version 11g release 1.

The four functions in this package are:

  1. UTL_MATCH.EDIT_DISTANCE returns PLS_INTEGER  – Use to see the number of characters which needs to be changed in first string to get second string
  2. UTL_MATCH.EDIT_DISTANCE_SIMILARITY returns PLS_INTEGER – In scale of 0 to 100 rate the match. 0 indicates no match and 100 indicates perfect match
  3. UTL_MATCH.JARO_WINKLER returns BINARY_DOUBLE – Same as EDIT_DISTANCE but ignores data entry errors.
  4. UTL_MATCH.JARO_WINKLER_SIMILARITY returns PLS_INTEGER – Same as EDIT_DISTANCE_SIMILARITY but ignores data entry errors.

All the four functions take two string argument as inputs.

Some examples:

select UTL_MATCH.EDIT_DISTANCE(‘PLSQL’,’SQL’) from dual; — This returns 2. Indicating that changing two characters in first string should get second string

select UTL_MATCH.EDIT_DISTANCE(‘HANG SENG’,’NASDAQ’) from dual;  This returns 7. Indicating that changing 7 characters in first string should get second string

select UTL_MATCH.EDIT_DISTANCE_SIMILARITY(‘PLSQL’,’SQL’) from dual; — This Returns 60.


For more info you can checkout following reference links:



Hope you find this informative and useful.

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Posted by on September 22, 2012 in Oracle, PL/SQL


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Weekly Participation Award for 31 August 2012 (PL/SQL Challenge)

Last updated on November 26th, 2014 at 07:07 am

Its my pleasure to share with you all that I am awarded “Weekly Participation Award for 31 August 2012” by PL/SQL Challenge.
The award is for the week ending 31 August 2012. The prize is O’Reilly Media Oracle eBook of my choice.

Visit my public profile on PL/SQL Challenge for other achievements


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Posted by on September 1, 2012 in Oracle, PL/SQL


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