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...Oracle Application Express...

  1. What is Oracle APEX?
  2. Are there any limitations in using Oracle XE?
  3. How do I backup and restore an Oracle XE Database?
  4. How to make applications portable?
  5. Should static files be placed in the database?
  6. How do I separate development from production environment?
  7. Which platforms are supported by Oracle Application Express?

1. What is Oracle APEX? Page Top
Oracle Application Express (Oracle APEX), formerly called HTML DB, is a rapid web application development tool for the Oracle database.
Oracle Application Express is different from Oracle XE. Oracle XE is the Express Edition of the Oracle Database that is front ended with a limited version of Oracle Application Express.
However, you can use Oracle Application Express on any flavour of the Oracle DB (Standard or Enterprise Editions as well), and your size is only constrained by the size of our DB.
2. Are there any limitations in using Oracle XE? Page Top
XE is free but Oracle has built certain limitations into the product.
The first limitation is memory. Oracle Database XE can address only 1GB of RAM. This limitation mainly affect how many users can access the database concurrently and how well it performs.
The second limit is that XE will only use one CPU. XE will run on a multi-CPU computer but won't scale up to use those CPUs. This functionality requires Oracle Database Standard Edition or Enterprise Edition.
The third limit is that only a single XE database can run on any given computer. You do not need a database for each application. Instead, Oracle uses the concept of schemas to separate applications.
Finally, a 4GB limit is enforced on disk space. 4GB is a huge amount of storage for most applications. You can also use APEX to link to other databases (on other servers) for more storage as needed.
3. How do I backup and restore an Oracle XE Database? Page Top
Backing up and restoring Oracle Database XE is based on protecting the physical files that make up the database:
There are 6 files in C:\oraclexe\oradata\XE: CONTROL.DBF, SYSAUX.DBF, SYSTEM.DBF, TEMP.DBF, UNDO.DBF and USER.DBF.
The control file SPFILE is in C:\oraclexe\app\oracle\product\10.2.0\server\dbs.
If in ARCHIVELOG mode, the redo log files should be backed up. Two redo log files are in C:\oraclexe\app\oracle\flash_recovery_area\XE\ONLINELOG.
Cold back up is when you stop the database and zip up all those 9 files (in NOARCHIVEMOD). When you restore the database copy all 9 files back to the same folders.
If the application is in ARCHIVEMOD and should run 24X7 then use hot backup.
4. How to make applications portable? Page Top
To ensure application can easily be moved from one Application Express environment to another you should avoid hard coded references to values that may change between environments.
For example, the application ID is often referenced in URLs throughout an application.
The Application Express engine uses the application ID to uniquely identify the application fetched and run from the application repository. Rather than using the actual application ID as is done in the URL below:
It is recommended to use an indirect reference instead:
Here, &APP_ID. is a built in substitution string that replaces the hard coded value 100. Using this technique, no modifications have to be made prior to deployment, even if the application ID changes.
Similarly, to ensure smooth deployment, references to images in templates, HTML regions or SQL queries should use substitution strings in stead of hard coded paths.
Consider, for example, an application whose images are stored on the file system in the virtual path /dev/images/ in a development environment and /prod/images/ on the production server.
Use substitution strings at the application level to avoid having to make changes throughout the application before deployment. E.g., define substitution string IMAGE_PATH, and give it a value of /dev/images/
5. Should static files be placed in the database? Page Top
Application Express applications may reference additional external files such as cascading style sheets (CSS), images and Javascript libraries.
These images can either be placed on the file system of the server that runs the web server or, when they are uploaded using Application Expressís application builder, can be stored inside the database.
A benefit of managing files such as images and CSS in the database with the application builder is that they can be exported and imported into another Application Express environment or workspace using only a browser.
However, storing related files in the database is recommended only when you have relatively few images and when the application is not expected to endure high request throughput.
When images, CSS and Javascript libraries are stored in the database, a database connection is established each time the browser requests one of these files.
In a high throughput application this may result in undue and unwanted strain on the database.
6. How do I separate development from production environment? Page Top
Depending on requirements for the availability of the application, the size of the user population and other factors you can decide how to divide the development environment from the production environment.
For certain applications, it is acceptable to combine the development server with the deployment server, as long as the end users understand that sometimes the application is not available.
Other applications may require two (development and production) or even three (development, test and production) servers.
In Application Express applications can be moved from environment to environment using an export and import facility for application definitions.
With one server available to run the database and Application Express, you can still separate the development version of an application from its production version by using two workspaces accessing separate schemas.
In this case one workspace will be used by developers and the other will be the workspace in which the application is deployed in production.
7. Which platforms are supported by Oracle Application Express? Page Top
Oracle Apex works on the following operating systems:
  • Linux x86
  • Mac OS X Server
  • Linux on Power
  • Linux x86-64
  • z/Linux
  • Linux Itanium
  • Solaris x86
  • Solaris Operating System (SPARC) (64 bit)
  • Microsoft Windows (32-bit)
  • Microsoft Windows (64-bit Itanium)
  • Microsoft Windows (x64)
  • AIX5L
  • HP Tru64 UNIX (Compaq / DEC)
  • HP-UX Itanium

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