Re: QRCVDTAQ

On 7/2/06, Larry Bolhuis <lbolhuis@xxxxxxxxxx> wrote:

I believe it was John Sears that spoke at a COMMON conference long ago
where I learned this. While waiting on a *DTAQ the job uses no resources
at all. It could sit there for weeks without using so much as a cycle.
Only when the wait timer expires and control transfers back to the
calling program does it use any cycles.  The actual reading and writing
to queues is also impressively quick and as I recall uses only a few MI
instructions for each read or write.

As I remember John explained that i5/OS (OS/400 back then) uses queues
extensively and therefore is very efficient at doing so.

*DTAQs are still my favorite i5/OS object. One object SOOO Many uses!

You can make a strong case that data queues have no place in
application systems. For programmers they are the system level
equivalent of the computer language GOTO.  They dont work well with
the debugger. They dont throw exceptions so errors go undetected.
They also violate the rule of isolating a user's job from the shaky
code being run by another job. Security wise consider this: how wise
would it be to implement a personnel or accounts payable system using
data queues? Where payment to a vendor was triggered by sending an
entry to a data queue?

-Steve