Re: Journaling without commitment control (WAS iSeries and SSD drives)

[Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx>]

Hi

This is what I remember - this article.

It seems to say you add the COMMIT keyword in your RPG. You STRCMTCTL in 
a CL wrapper, then ENDCMTCTL after the call to the RPG returns.

But I didn't see anywhere about using a commit or rollback - is that 
what you mean you "have to use it"?

Thanks
Vern

On 1/18/2013 2:12 PM, Charles Wilt wrote:
> Close, you turn it on but you actually have to use it...
>
> The exact quote from Rick's paper:
> Though most database and other write operations are asynchronous, database
> journal receiver write operations are usually synchronous to the issuing
> job. This means the job is forced to wait (in the system’s disk I/O write
> functions) for the I/O (write) to complete before it continues processing.
> The SLIC Journal functions can do the journal writes asynchronously if the
> job uses commitment control.
>
> When commitment control is in effect, the database journal write functions
> know that file integrity is required only at a commit boundary and not at
> every record update/add/delete operation. Because of this, the database
> journal writes are scheduled asynchronously. When a commit boundary is
> reached, the database functions ensure that all pending database file I/O
> is complete before continuing.
>
> Lab tests show that using commitment control and journaling yields
> performance almost equal to not using database journaling. If you use
> journaling but not commitment control, a job can be *three to four times
> slower* than when you don’t use journaling at all.
>
> “But this means I have to change my code!” you say. True, but the cost of
> the changes are minimal compared to the performance benefit. In the CL
> program that calls the batch program, specify the files that use commitment
> control and open them. Start a commit cycle in the CL program before
> calling the batch program. In the application program(s), change the file
> description to specify that commitment control is in use. Once the program
> returns to the CL program, end the commit cycle to force any pending file
> I/O to complete.
>
> The version of the paper I have has a side bar by Larry Youngren taking
> about what is now option 42...
> The Batch Journal Caching PRPQ can help you avoid the problems and costs
> associated with making application changes (such as adding commitment
> control) to improve performance in batch environments.
>
> Charles
>
> On Fri, Jan 18, 2013 at 2:57 PM, Vernon Hamberg <vhamberg@xxxxxxxxxxxxxxx>wrote:
>
> > Maybe it's that you just turn on commitment control in a job, then never
> > actually commit or rollback anything. Then turn it off after you're done.