The following are the advantages of choosing Oracle Database.
Portability
Oracle is ported to more platforms than any of its competition, running on more than 100 hardware platforms and 20 networking protocols. This makes writing an Oracle application fairly safe from changes of direction in hardware and operating system, and therefore a safe bet. One caveat, however, is that applications using some constructs (such as field level triggers) may have to be reworked when porting them to a block mode environment. You can also develop a fairly fully featured application with little knowledge of the underlying OS. Personally, I have developed applications on OS systems barely knowing how to copy and edit text files.
Market Presence
Oracle is by far the largest RDBMS Vendor, and spends more on R&D than most of its competitors earn in total revenue. Oracle has the largest independent RDBMS market share in VMS, UNIX and OS/2 Server fields. This market clout means that you are unlikely to be left in the lurch by Oracle and there are always lots of third party interfaces supported and also, proficient staff are relatively easy to get.
Version Changes
Oracle seem very good at informing you in detail as to what is not going to be supported in the next major release and usually have some knob you can twiddle for good backward compatibility, or simply leave it working, but with "don't use this, use xxxx instead" warnings in the manual. Backward compatibility is very good meaning you will not be in for an application re-write when you upgrade the DBMS. [Compare this with the Ingres v5->6 OSQL upgrade from hell.] I've worked with Oracle since V4 Beta and have never been in for nasty surprises as far as syntax goes. However, see "Version Changes" under disadvantages.
Backup and Recovery
Oracle provides industrial strength support for on-line backup and recovery and good software fault tolerance to disk failure. You can also do point-in-time recovery. Of course, you need the archive mechanisms and storage space to do this, but Oracle supports continuous archiving to tape devices spanning multiple volumes.
Performance
Speed of a *tuned* Oracle database and application is quite good, even with large databases. Oracle refer to >100 GB databases and have personal experience administering 10 GB databases. The performance is not only "raw", but includes consideration of performance with locking and transaction control.
Cursor Support
Oracle, like Ingres, but unlike Sybase (until Release 10 I think),supports cursors which ease programming when performance is needed. A cursor basically lets you do row-by-row processing. Oracle supports multiple cursors per Oracle connection in line with ANSI standards.
SQL Dialect
The dialect of SQL offered by Oracle is in my opinion superior to the others in the extensions it offers over ANSI-2, which is very much a lowest common denominator. Constructs such as the absolute function and decode keyword are very powerful Oracle additions to the standard SQL.
Multiple Database Support
Oracle has a superior ability to manage multiple databases within the same transaction using a two-phase commit protocol. This is best implemented in V7. You can fairly easily move where data is actually stored from node to node in a network and have data mirroring, making it easy to optimise the location of the data from time to time. This is not so easily done with offerings from other vendors or earlier versions of Oracle, where you were not able to update more than one database in the one transaction with any reliability. This meant that you could not move data around without recoding your programs. With V7, your DBA can optimise the location without pre-planning by programmers or re-examination of the code prior to the move.
PL/SQL
PL/SQL, the procedural extensions, is a draft ANSI standard for procedural DBMS languages. See main discussion on PL/SQL.
Declarative Integrity
Oracle V7 onwards supports declarative database integrity (the current ANSI standard) and V6 permits you to enter the declarations. With V6, you can get the toolset (such as SQL*Forms 3) to read the declarations and automatically generate the required code. With V7 onwards, not even this is required, as the database engine automatically enforces the integrity. This means that you can open up your database to end-users through simple third party interfaces as they simply cannot break your business rules even if they try. It makes it easy to administer changes in business and data rules as there is only one spot where the change needs to be made. This lowers the cost of required modification to the system because you do not have to edit all applications code that works with the table.
It is reasonable to expect Oracle to release the first SQL-93 implementation at near-full compliance. As one DBA noted on the net recently "With Oracle V8 onwards I'll be out of a job because everything will be in the pfile".
