Re: QJOCHRVC

["Charly Jones" <charly301@xxxxxxxxxxx>]

> From: Lyle.Hart@xxxxxxxxxxxxxxx
>
> I attended a performance class in Rochester 2 weeks ago.  The system pgm
> QJOCHRVC was mentioned.  This pgm has a default parm of 50000, it was
> recommended to change this to 1-2 million.
>
> This pgm controls how often changes to journaled objects are forced to
> disk.
>
> Has anyone made this change?
>
> IBM said more info will be available at v5r3.

This API is available back to V4R5...  There is a redbook called: 'Striving 
for Optimal Journal Performance'
that contains a full explanation of the API and side-by-side benchmarks with 
performance numbers.  Here are some notes I got from a Google search using 
QJOCHRVC:

You can now tune the journal recovery ratio (V4R5)
Background SLIC tasks: JORECRA (one per journal)
Sweep through main memory writing changed pages of journaled objs
Their mission is to cap the quantity of recovery time in the event of a 
crash
The more journaled objects, the more aggressive these tasks become
They are driven by a "Recovery Ratio"
The default ratio is 50K
The tasks wake up as soon as 50K/ Numb_ Objs more Jrn Entries arrive
Every extra 10K added to the ratio increases abnormal IPL time by about 30 
seconds
The higher the ratio, the less frequently journaled objects get written and 
the
better the run time performance vs. longer potential IPL
It's similar to a default "Force Write Ratio" for journaled files
New API: Call QJOCHRVC 1000000
Increases recovery ratio to 1 Million (reduces background load by 95%)
Legal range is 10K to 2 Billion

Charly Jones
Gig Harbor WA
253 265-6244

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