DB2 is the database management system from IBM. Currently it has the
second largest market share of the “big three” RDBMS. Oracle is the
first and SQLserver a distant 3rd, although SQLserver is growing by
leaps and bounds. DB2 is installed automatically with system I operating
system, and has many benefits from being integrated with the O.S.
There is a little jargon that is particular to DB2. First and most
important is a “Physical File” which is a table in the database. One
thing that I am not a fan of is the fact that there is not a way to do
referential integrity though such things like foreign keys. Of course
there is easy ways to make unique keys, or it would not function as a
Database.
Second is a “Logical File”, which is built off of
physical files and works all lot like a view in SQLserver. A logical
file is a “sorted path” or saved query result. If you have a PF or
several that get joined together a lot, you should build a logical file
to speed up data retrieval. Logical files can be used to update a
physical file as long as the logical file only accesses one PF and not a
join of two or more PFs.
