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  3. April 2013

RE: Multiple Inserts - does block writing occur?

Correct, the physical and its logicals are not Unique. The test was performed using files created with DDS. The In my test I didn't want to introduce additional variables - since the current programs today use a DDS file and they block. I wanted to see the difference between DDS blocking and DDS non-blocking.

-Kurt

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Tuesday, April 16, 2013 12:40 PM
To: Midrange Systems Technical Discussion
Subject: Re: Multiple Inserts - does block writing occur?

Note it's not just the table itself. If any unique indexes or logical files exist over the table the DB will not block the writes.

Charles


On Tue, Apr 16, 2013 at 11:25 AM, Anderson, Kurt <KAnderson@xxxxxxxxxxxx>wrote:

The table doesn't have a unique key in the tests I ran.

-Kurt

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Thursday, April 11, 2013 3:43 PM
To: Midrange Systems Technical Discussion
Subject: Re: Multiple Inserts - does block writing occur?

If the table has a unique key, then RPG won't do block i/o as the DB
needs the records to check for uniqueness.

HTH,
Charles




On Thu, Apr 11, 2013 at 3:40 PM, Anderson, Kurt
<KAnderson@xxxxxxxxxxxx
wrote:

I'm not sure I can apply blocked inserts here w/o getting overly
complex - but I'm not counting it out.

That said, I tried testing to see the difference between blocking
and not blocking, and I did not get the results I was expecting.
Essentially they took the same amount of time. To keep it simple, I
was
changing our native
RPG I/O from using blocking to specifying Block(*No). Inserted
1,000,000
records and it took 21 seconds with blocking on and off. I suppose
I should figure out what I want to do, run a huge test to see if
variance (if
any) to run the process is acceptable.

Dan, thanks for the note on the unique index thing. I have the
table defined with a primary key (which presumably creates an
underlying index), so the table will be unique (it wasn't before).

-Kurt

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Thursday, April 11, 2013 8:40 AM
To: Midrange Systems Technical Discussion
Subject: Re: Multiple Inserts - does block writing occur?

If you want to enforce blocking from the SQL statement level, you'd
have to do it as a "blocked insert." aka "insert multiple rows"

INSERT INTO DEPARTMENT (DEPTNO, DEPTNAME, ADMRDEPT) VALUES ('B11',
'PURCHASING', 'B01'),
('E41', 'DATABASE ADMINISTRATION', 'E01')

INSERT INTO CORPDATA.EMPLOYEE
(EMPNO,FIRSTNME,MIDINIT,LASTNAME,WORKDEPT)
10 ROWS VALUES(:DSTRUCT:ISTRUCT)

For best performance, if you table is journaled, make sure you are
using commitment control and not commiting after every record.
Ideally, you'd want just under 128K of journal entries before commiting.

Charles






On Wed, Apr 10, 2013 at 1:22 PM, Anderson, Kurt
<KAnderson@xxxxxxxxxxxx
wrote:

I think I found my answer in
http://publib.boulder.ibm.com/infocenter/iseries/v5r4/topic/rzajq/
rz aj q.pdf Under "Control database manager blocking"

"The SQL run-time automatically blocks rows with the database
manager in the following cases:
INSERT
If an INSERT statement contains a select-statement, inserted rows
are blocked and not actually inserted into the target table until
the block is full. The SQL run-time automatically does blocking
for blocked inserts.
Note: If an INSERT with a VALUES clause is specified, the SQL
run-time might not actually close the internal cursor that is used
to perform the inserts until the program ends. If the same INSERT"

So it sounds like in my case, where I'd be doing inserts using
Values, that blocking wouldn't really be occurring. I'm not sure
how to interpret the bit about the internal cursor.

However it does say we can control blocking by using OVRDBF and
SEQONLY - which we actually currently do. So if it obeys the
override in term of blocking the write, then I should be set.

Ultimately I could run a test of a huge number of records, so I
figure I'll get that on my to-do list.

-Kurt


-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:
midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Anderson, Kurt
Sent: Wednesday, April 10, 2013 11:17 AM
To: 'Midrange Systems Technical Discussion'
Subject: Multiple Inserts - does block writing occur?

Continuing down the SQL path...

If I execute 100 individual insert statements to a table (no
commitment control), does the system insert each record out
individually, or does blocked inserting occur?

A little background:
We receive files with all sorts of layouts, and we mediate them
and output them to our standard file. The mediation programs have
a lot of similarities, and I have moved most of those similarities
into service programs. However one thing they all still share is
that each program is writing to the standard file. I'd like to
encapsulate that
standard file.
In doing so, I'd like to use SQL to write the records, but I
can't sacrifice blocked writing due to the high volume of transactions.

I'm aware of inserting multiple rows in one statement using
arrays, however I don't want to attempt to control the number of
records the system should write out at once. In addition, there
will already be an element of complexity using arrays because one
incoming record may result in more than one standard record (so
doing a blocked insert for that situation would be fine).

I'm on IBM i 7.1.

Thanks,
Kurt Anderson
Sr. Programmer/Analyst
CustomCall Data Systems, a division of Enghouse Systems Ltd.
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