On 3/04/2016 2:50 PM, Andrew Rowley wrote:
On 02/04/2016 10:09 PM, David Crayford wrote:
IBM switched the magic bit to offload the JZOS JNI C/C++ workload to
a zIIP so they could do the same for DFSORT. A well engineered library
could handle the callbacks so the client just reads records like a
normal API. That would certainly push Java batch up a notch.
One question that puzzles me (maybe it's my lack of an application
programming background): Why is sort used so much on z/OS?
Good question! Sort can be utilised for other purposes than sorting, it
can be used as an I/O engine. DFSORT (or Syncsort) implements bespoke
highly optinized I/O using low-level programming interfaces such as
chained EXCPs which are significantly faster than using standard access
methods like QSAM or BSAM, including overlapping BSAM I/O. DFSORT has
exit routines (callbacks) which get called for each record. Basically
it's supercharged I/O. One of our products does just that as do many
others. IIRC, IBM FileManager uses sort for I/O. The trouble with using
this technique with Java is the JNI/callback overhead.
I know you can then e.g. do grouping based on key changes, but is that
really necessary in current programs? Is that the reason it is
commonly used?
I generally use e.g. Java HashMap, C# Hashtable for grouping so the
data doesn't need to be sorted. Do other common languages on z/OS
provide similar functions? (C++ I know.) Are there opportunities to
use programming language features to avoid sorts altogether?
Andrew Rowley
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