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IDS Forum

Re: Isolation modes in mach11 cluster

Posted By: Art Kagel
Date: Friday, 30 August 2013, at 1:22 p.m.

In Response To: RE: Isolation modes in mach11 cluster (Justin Killen)

Are you sure the column type for the serial_num column is SERIAL and not
SERIAL8 or BIGSERIAL (those types would require a different DBINFO
function)? The DBINFO() call should always work if it is run immediately
after the INSERT to the table containing the SERIAL column.

Art

Art S. Kagel
Advanced DataTools (www.advancedatatools.com)
Blog: http://informix-myview.blogspot.com/

Disclaimer: Please keep in mind that my own opinions are my own opinions
and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
other organization with which I am associated either explicitly,
implicitly, or by inference. Neither do those opinions reflect those of
other individuals affiliated with any entity with which I am affiliated nor
those of the entities themselves.

On Fri, Aug 30, 2013 at 12:46 PM, Justin Killen <
jkillen@allamericanasphalt.com> wrote:

> When we do this:
>
> SELECT DBINFO( 'sqlca.sqlerrd1' ) FROM sysmaster:sysdual;
>
> We always get 0. This is on windows ODBC driver, 3.50.TC8
>
> -Justin
> -----Original Message-----
> From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of Art
> Kagel
> Sent: Thursday, August 29, 2013 7:07 PM
> To: ids@iiug.org
> Subject: Re: Isolation modes in mach11 cluster [31310]
>
> Yeah, this:
>
> SELECT serial_num FROM infx_cluster_test WHERE serial_num = (select
> max(serial_num) from infx_cluster_test)
> Commit Transaction
>
> Is WRONG WRONG WRONG and very dangerous! You are VERY likely to get a
> serial value inserted by another user session, especially if you turn on
> the READ_COMMITTED isolation option! Instead do this:
>
> SELECT DBINFO( 'sqlca.sqlerrd1' ) FROM sysmaster:sysdual;
>
> Art
>
> Art S. Kagel
> Advanced DataTools (www.advancedatatools.com)
> Blog: http://informix-myview.blogspot.com/
>
> Disclaimer: Please keep in mind that my own opinions are my own opinions
> and do not reflect on my employer, Advanced DataTools, the IIUG, nor any
> other organization with which I am associated either explicitly,
> implicitly, or by inference. Neither do those opinions reflect those of
> other individuals affiliated with any entity with which I am affiliated nor
> those of the entities themselves.
>
> On Thu, Aug 29, 2013 at 8:00 PM, Justin Killen <
> jkillen@allamericanasphalt.com> wrote:
>
> > 1) table lock level is row locks, SQL for each test iteration is as
> > follows:
> >
> > Begin Transaction
> >
> > INSERT INTO infx_cluster_test (host_name, id, data) VALUES ('JUSTINK-PC',
> > 756,
> > 'fp''L+h2$}vxV6NPjS;GKZZp/upua"V')
> >
> > SELECT serial_num FROM infx_cluster_test WHERE serial_num = (select
> > max(serial_num) from infx_cluster_test)
> > Commit Transaction
> >
> > This SQL is part of a base level data access layer that most every insert
> > uses. It works flawlessly on our current single-system setup with
> > USELASTCOMMITTED=NONE and SET LOCK MODE TO WAIT 2.
> >
> > 2) We tried setting USELASTCOMMITTED to ALL, but the result is that some
> of
> > the selects are not coming back with correct data (client A does the
> > insert 3,
> > then client B does an insert and a select max(serial_num), then client A
> > does
> > a select max(serial_num), resulting in client A getting client B's data).
> > I'm not sure exactly what the difference is between ALL and COMMITTED
> READ,
> > and inline comments in onconfig seems circular - if anybody could shed
> some
> > light on the differences between the 4 options, that would be helpful.
> >
> > 3) We like the idea of setting the CLUSTER_TXN_SCOPE option to cluster,
> but
> > how does this effect things if the WAN link goes down to the RSS?
> >
> > -Justin
> >
> > -----Original Message-----
> > From: ids-bounces@iiug.org [mailto:ids-bounces@iiug.org] On Behalf Of
> > Fernando
> > Nunes
> > Sent: Thursday, August 29, 2013 3:38 PM
> > To: ids@iiug.org
> > Subject: Re: Isolation modes in mach11 cluster [31307]
> >
> > Hmmm.... several important points:
> >
> > 1-I have some doubts (sorry if I'm mistaken) that you don't see the same
> > behavior on just one (primary) server. What is your table lock level, and
> > how is the query accessing the table?
> > 2- If you want to try USELASTCOMMITTED you can set it to "Committed
> Read".
> > It shoudl not cause your application any harm. But your lock level must
> be
> > "row"
> > 3- Depending on your version look for CLUSTER_TXN_SCOPE (
> >
> >
> >
> >
>
>
> http://pic.dhe.ibm.com/infocenter/idshelp/v117/topic/com.ibm.adref.doc/ids_adr_1165.htm
> > ).
> > It allows you to define when your application recieves the
> > confirmation
> > of the COMMIT (can be when it's completely replicated across the cluster)
> >
> > Regards
> >
> > On Thu, Aug 29, 2013 at 11:15 PM, Justin Killen <
> > jkillen@allamericanasphalt.com> wrote:
> >
> > > All,
> > >
> > > We are in the process of converting from a single database server to a
> > > cluster, and we are having some confusion about transactions and
> > isolation
> > > levels. Our cluster consists of a primary and secondary HDR that are in
> > the
> > > same location (1gbps) and an RSS that is across a WAN link (4.5mpbs) We
> > > designed a test app to run against the cluster (not yet in production,
> > but
> > > with a copy of the production data) to verify it is working as we
> expect.
> > > The
> > > program basically does this:
> > >
> > > 1) Choose a server randomly (either primary, secondary HDR, or RSS)
> > > 2) Begin transaction
> > > 3) Insert/update/delete on test table: infx_cluster_test
> > > 4) (on case of insert, do a select to get back a serial number)
> > > 5) Commit transaction
> > > Foreach server:
> > > 6) Select from infx_cluster_test and verify the data is what we just
> > > changed
> > > it too. If it doesn't match, keep trying until it does. Here, we record
> > how
> > > many attempts were made, and the time-lapse between the initial
> > > insert/update/delete and the successful verification select.
> > >
> > > Now then, we set up this program to run from a single computer, and it
> > > works
> > > pretty well. However, when we run it on multiple computers, we get
> into a
> > > scenario where each clients is connected to a different server and each
> > of
> > > them has begun a transaction, performed an insert, and is trying to
> > > perform a
> > > select (step 4). What we get here is the strange part. On one
> connection,
> > > we'll get error code 245 (could not position within a file via an
> index),
> > > and
> > > on the other we'll get error code 246 (could not do an indexed read to
> > get
> > > the
> > > next row). It was suggested to us to change our USELASTCOMMITTED
> onconfig
> > > value from NONE to ALL, but we're unsure of the implications of doing
> so,
> > > or
> > > what side-effects it might have (the current default value within the
> > > onconfig.std is set to NONE, so that's how we left it).
> > >
> > > Is there a standard setup that is commonly in use for mach11 clusters
> and
> > > isolation modes?
> > >
> > > Thanks,
> > > -Justin
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
> *******************************************************************************
> > > Forum Note: Use "Reply" to post a response in the discussion forum.
> > >
> > >
> >
> > --
> > Fernando Nunes
> > Portugal
> >
> > http://informix-technology.blogspot.com
> > My email works... but I don't check it frequently...
> >
> > --001a11c22e58a1772d04e51dc04e
> >
> >
> >
> >
>
>
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
> >
> >
> >
>
>
> *******************************************************************************
> > Forum Note: Use "Reply" to post a response in the discussion forum.
> >
> >
>
> --001a1133aa86353ee404e520ad83
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>
>
> *******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>

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