Dirty read in VSAM.

[Raghwan]

For a recent interview, I was asked a question which I am quite sure about. What is a dirty read in VSAM? Have you ever used the "dirty read" technique?

I could not answer this question. I have searched and find out that the "dirty read" technique can be used to provide a high degree of concurrent access to VSAM files while avoiding the complications associated with CI and CA splits. If it's a technique, why it is called "dirty"? Technique should be widely accepted... can some one please help me understaning the answer for this question.

[Robert Sample]

Go to http://www.redbooks.ibm.com and find the VSAM Demystified Redbook. Download it and read it to answer many VSAM questions. From this book:

With batch programs using RLS, you have a choice of two ways of handling read integrity. The
default is no read integrity (NRI) where record locks are not obtained for a read. This
configuration means that you can read a record and get uncommitted data that might be
backed out. This is sometimes called a dirty read. The other option is to ask for a consistent
read. In this case, RLS ensures that the read request waits until updates for that record are
committed.