Apr 15 2013

Oracle Database Gateways 11g R2 (11.2) Installation and Configuration for heterogeneous connection from Oracle to Microsoft SQL database

Category: 11g,Databaseittichai @ 5:33 pm


Install the Oracle Database Gateways 11g R2 (11.2). See the screen snapshots of the installation here.


  • During the installation, the following+ default initialization parameter file is created:
dg4msql = Database gateway for Microsoft SQL Server. 
If you choose a different database option, use the appropriate path name.
  • Copy initdg4msql.ora to a new file init[MSSQL].ora.
[MSSQL] can be any meaningful name easier to refer to, for example, mssqlsale. 
The filename will be in the format of init[MSSQL].ora.
copy initdg4msql.ora initmssqlsale.ora
  • Modify newly created file initmssqlsale.ora and modify or add the MS SQL server & database name.
# This is a customized agent init file that contains the HS parameters
# that are needed for the Database Gateway for Microsoft SQL Server
# HS init parameters
  • Modify the listener.ora file. This can be that of the existing listener or new listener. Add SID_DESC to the appropriate place in the listener.ora file.
[MSSQL] =  Name of the new configuration file excluding the init and .ora.
For example, if the file name is initmssqlsale.ora, the [MSSQL] will be only mssqlsale.
[ORACLE_DG_HOME] = Oracle Database Gateway Home. This is NOT listener home.
[DRIVER] = dg4msql for Microsoft SQL Server


        (ADDRESS = (PROTOCOL = TCP)(HOST = DGHOST)(PORT = 1521))

  • Restart or reload the listener.
  • Validate using lsnrctl status.
C:\>lsnrctl status
LSNRCTL for 64-bit Windows: Version - Production
Services Summary...
Service "mssqlsale" has 1 instance(s).
 Instance "mssqlsale", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully
  • On different Oracle database where we’d like to connect to this MS SQL database, create a new database link. The new database link will point to the the host where the gateway is installed.
create database link dblink_mssqlsale connect to "username" identified by "password"
using '
DGHOST = Host where the Oracle Database Gateway is installed.
mssqlsale = SID name mentioned in the listener.ora.
  • Try to query for a table.
select count(*) from information_schema.tables@dblink_mssqlsale;

Add more MS SQL databases

  • Repeat the above steps starting with copying the sample file into a new init file, and updating it with an appropriate host and database name.
copy initdg4msql.ora to initmssqlhr.ora
  • Update the listener.ora.
  • Restart or reload listener. Check using lsnrctl status.

Nov 09 2011

Customize/Personalize Oracle APEX Workspace Environment

Category: 11g,APEX,Browser,Tool,URLittichai @ 4:06 pm

When you have multiple Oracle APEX environments, e.g., development, test, UAT and production, and for multiple groups, one of the confusing things is that sometimes developers are lost on which environment they’re working on. Most of technically proficient developers can make a distinction easily from the URLs they’re currently using. However, most of less technically proficient (e.g., business users) sometimes cannot.

A quick and simple solution here is to make a visual distinction on the APEX workspace pages especially on the logo area. Instead of using plain vanilla logo images, they are replaced with more distinct and informative images.

This is the default APEX workspace logon page.

Default Workspace Logon Image

This is a sample of the personalized workspace logon page with a company logo and it is showing that this is the development environment.

Customized APEX workspace logon page

This is the main workspace page after logon showing the default logo image.

Default Workspace Page

You can change it to be like this.

Customized APEX workspace development page

With just this minor change, our users feel more comfortable knowing that they’re working the right environment.

How to change it?

With a quick investigation, you can easily find the paths of those image files as follows:

Workspace logon page:

Image path: /i/apex/builder/apex-logo-white.gif
Image size: 300px x 30px
Transparent background

Image path:/i/apex/builder/apex-db-apps.png
Image size: 240px x 200px
Transparent background

Workspace main page after logon:
Image path: /i/htmldb/apex_logo.gif
Image size: 300px x 30px
White background

  • Use Photoshop or any image editing tools to recreate those image files.
  • Copy and replace those image files on the web server. Please make the backup of those files before replacing them.

Note that this approach will NOT work if you’re using a shared web server for multiple APEX database environments because they’re using the same image files.

Update: Using ApexLib script in the login message (under Manage Instance) as mentioned by Peter in the comment section is another solution for customization. I like this approach as not only you can customize the logo, but you can also change the description text on the workspace logon page. In addition, since the change is on the APEX instance itself, it can definitely be used on a shared web server.

Aug 15 2011

Book Review: Oracle 11g R1/R2 Real Application Clusters Essentials by Ben Prusinski and Syed Jaffer Hussain (Packt Publishing)

Category: 11g,Databaseittichai @ 9:31 pm

Oracle 11g R1/R2 Real Application Clusters EssentialsOracle Real Application Cluster (RAC)  becomes the technology of choice for highly available and highly scalable deployment of enterprise Oracle database environment. With its innovative technology it comes with no surprise its complexity. The complexity is not only with the underlying database technology itself, but also how well you design and implement it to work with other components including operating system, storage subsystem, etc. In order to setup and maintain a successful RAC environment, it not only requires technical knowledge of database administrator (DBA), but also well collaboration and extended planning between all IT and business partners.

Few years back, there has been a movement of DBA 2.0 which says that, in addition to database knowledge,  an extended understanding of operating system, storage and/or networking is encouraged due to more tightly integrated of Oracle database technologies such as Clusterware, RAC, ASM with the underlying subsystems. I agree with this notion but not to the extent that DBAs should perform all works in those areas. (Yes, I’m aware that some DBAs do it all.) However, I think at least they should have enough understandings of all-related technologies to collaborate with those who are responsible for in order to achieve the desired setup. In many cases especially in the large companies where traditional organization division of the job description of administrators is clear cut and no overlapping, being well-rounded with all-related technologies will allow DBA to better discuss the requirements and designs and even assist with the implementation details.

Most Oracle RAC books in the market today tend to focus only on the detailed technical aspects of this database technology. This mainly is good for those Oracle professionals who at least have worked with RAC before. Few books really provide a good foundation for those who are new to this technology. One of those few which I’ve just read recently is Oracle 11g R1/R2 Real Application Clusters Essentials authored by Ben Prusinski and Syed Jaffer Hussain published by Packt Publishing.

What I really like about this book is the fact that it does not jump into the nuts and bolts of this Oracle technology right away but instead it is trying to build up good foundation starting from concept (especially high availability), architecture (of all components not just of database), design, implementation and then even some of the real-world samples. This stepping-stone approach helps readers to understand what is involved and how they should deploy this technology for the high available database.

In the chapter 1, the emphasis of the high availability concept is crucial. The authors precisely points out that high availability should be looked from users’ perspective. Many DBAs or system administrators especially novice ones have a tendency to focus solely on their respective areas. The provided sample of the availability percentage in the “high availability interpretations” section is a good reminder for a need to have an end-to-end high availability design to avoid a single point of failure (SPOF). The chapter goes on to give the definitions of many acronyms (BIA, BCP, DRP, etc.) commonly-used during the planning phase. It is quite useful to be aware of them especially when discussing with business end-users. The chapter ends with providing a whole picture of the high availability solutions (RAC, Data Guard, Streams, Application Server Clustering) from Oracle as a part of the Maximum Availability Architecture (MAA). It is worth to point out that RAC is just one (not the only) of key components for a complete high availability solution.

Chapter 2 looks into the hardware components of Oracle RAC architecture including network, storage, etc. Again, I think the authors reinforce a need to understand all these underlying technologies (at least at high level) even though DBAs might not involve in the actual implementation. But it is crucial to have this knowledge under their belts in order to have the productive discussions of the requirements and design with system administrators.

Chapter 3 goes into the clusterware installation of 11g R1/R2. Even though readers may to be able to find similar information on many web sites and blogs, this book has some extra information which makes an attempt to explain what each action does, for example, what happen when the orainstRoot.sh and root.sh run?

Chapter 4 dedicates to the Automatic Storage Management (ASM) which becomes the only clear choice for storage management in the 11g deployment. The chapter covers all aspects of ASM in both R1 and R2 including new features, configurations, management, etc.

Chapter 5 covers Clusterware management and (some) troubleshooting samples. Instead of showing all possible troubleshooting scenarios (which is impossible to include everything in a chapter or even in a book), the authors did an excellent job of giving an overview of all necessary Clusterware utilities in order to troubleshoot the issues.

Chapter 6 turns our attention to RAC database administration. The structure is similar to that of Clusterware in the chapter 3. The latter part of the chapter also covers the automatic workload management including the topic of the service which is highly recommended to utilize it (not using the default database service.)

Chapter 7 covers all aspects of backup and recovery of Oracle database including the best practices. In addition, new features of RMAN in Oracle 11g R1 and 11g R2 along with OCR and voting disk backup and recovery are discussed.

Chapter 8 tries to give an overview of performance tuning. The intention here seems to just give an overview of the concept and methods of performance tuning as well as new 11g performance features, for example, Real Application Testing (RAT) which has the Database Replay and SQL Performance Analyzer (SPA). This high-level overview focus is understandable because the scope of performance tuning is generally vast. Some of tuning metrics especially relate to the wait events are explained here.

Chapter 9 focuses on the upgrade scenarios. As we all know it is impossible to cover all possible scenarios. But the authors gives sufficient information about overall upgrade processes from 10g R2 to 11g R1 and then to 11g R2 in this chapter. Definitely consulting with Oracle support for more details on individual upgrade case is still highly recommended.

Chapter 10 is very informative on the node addition and removal. The chapter steam-lines the steps pretty well (comparing to the official Oracle document which is very confusing at the first read with the flow of information). (We just went through adding two nodes into the existing two nodes of Oracle 11g R1 two months ago. That’s why I can say that.)

Chapter 11 shows the readers the importance of the end-to-end high availability implementation. The high availability should not stop at the Oracle RAC database, but it must extend to application layer on top of it. In addition to an overview of Oracle EBS (E-Business Suite), this chapter shows the readers how to take full advantage of high availability and performance features in Oracle RAC database.

The last chapter wraps up nicely with information about other tools in the MAA tool suite namely Streams and Data Guard. It covers all various topics of thes tools including concepts, new features, best practices, and overview configuration.

The last section of this book on the additional resources and tools is a nice read and very informative. It is just like a nice dessert at the end of a good meal.

In conclusion, if you’re new to Oracle RAC technology, this is THE book for you. It should give the readers enough understanding to jump on Oracle RAC bandwagon. Advanced DBAs may find that most of the contents in the book are too familiar, but they might be attracted to the new features, comparisons between R1 and R1 as well as some of real-world samples mentioned in this book. Overall I appreciate a very well effort of Ben ad Syed for one of the most complete informative books on Oracle RAC in the market today. Well-deserved kudos to them.

Thanks to Packt Publishing for the opportunity to review this book.

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Mar 21 2011

Differences between Native and Interpreted Compilations in Oracle 11g? Why Performance Is Improved in the Native Compilation?

Category: 11g,Databaseittichai @ 2:38 pm

Quick bullet points from reading the Transparent Performance Improvement: Real Native Compilation from the PL/SQL Enhancements in Oracle Database 11g white paper:

  • The PL/SQL is an interpreted language but it is not just like other interpreted languages , e.g. BASIC, where the code is processed statement by statement at the run time. The PL/SQL code is compiled into machine code called M-Code with a target virtual machine called PL/SQL Virtual Machine (PVM), just like Java to Java Virtual Machine (JVM).
  • The PVM is implemented as a set of subroutines in Oracle executables, and scans the M-Code at run time.
  • The scanning detects each successive OPCODE and its OPERANDS, then calls the subroutine that implements this OPCODE with actual arguments.
  • This run-time scanning of the M-Code takes some resources. This is where the PL/SQL native compilation will help with improvement.
  • Compilations of both follow the same path:
    • In the interpreted mode, the M-Code is produced.
    • In the native mode, a platform-specific dynamically linkable library (DDL) (similar to .dll in Windows or .so in Unix) is produced.
      • This platform-specific DLL, at run time, calls exactly the same PVM subroutines with same arguments as would have been called by scanning the M-Code.
  • In short, the performance improvement is due to the fact that the scanning effort has been moved from run time (when in interpreted mode) to compile time (when in native mode).
  • Since exactly the same PVM subroutines are called with exactly the same arguments in both interpreted and native modes, the native mode is guaranteed to have exactly the same semantics as the interpreted mode.

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