Qalias attributes

Discussion:

Qalias attributes

Bob Juch

2014-07-14 17:16:54 UTC

've been searching but can't find that IBM has documented this:

If a queue has an alias entry that is used for access and the two have
different attributes, e.g. persistent, which takes precedence?

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Sailesh Krishnamurti (BLOOMBERG/ 120 PARK)

2014-07-14 17:28:28 UTC

Permalink

I believe the base Queue attribute takes precedence and a log entry is written in the Qmgr AMQERR log.

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To: ***@LISTSERV.MEDUNIWIEN.AC.AT
At: Jul 14 2014 13:27:07

've been searching but can't find that IBM has documented this:

If a queue has an alias entry that is used for access and the two have different attributes, e.g. persistent, which takes precedence?
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Tim Zielke

2014-07-14 17:43:28 UTC

Permalink

I just did a quick test with a trace where the alias queue had a DEFPSIST(YES) which pointed to a target base queue whose DEFPSIST(NO) and ran the amqsput/amqsbcg samples on it. The message came out as persistent. So looks like the qalias DEFPSIST attribute took precedence.

Thanks,
Tim

From: MQSeries List [mailto:***@LISTSERV.MEDUNIWIEN.AC.AT] On Behalf Of Sailesh Krishnamurti (BLOOMBERG/ 120 PARK)
Sent: Monday, July 14, 2014 12:28 PM
To: ***@LISTSERV.MEDUNIWIEN.AC.AT
Subject: Re: Qalias attributes

I believe the base Queue attribute takes precedence and a log entry is written in the Qmgr AMQERR log.
----- Original Message -----
From: ***@LISTSERV.MEDUNIWIEN.AC.AT<mailto:***@LISTSERV.MEDUNIWIEN.AC.AT>
To: ***@LISTSERV.MEDUNIWIEN.AC.AT<mailto:***@LISTSERV.MEDUNIWIEN.AC.AT>
At: Jul 14 2014 13:27:07
've been searching but can't find that IBM has documented this:

If a queue has an alias entry that is used for access and the two have different attributes, e.g. persistent, which takes precedence?

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Dominique Courtois

2014-07-14 17:56:06 UTC

Permalink

Hi,
The general rule should apply : the object named by the application (alias) is used
Regards
Dominique

----- Mail original -----
De: "Tim Zielke" <tim.zielke-PR+tvw7B/***@public.gmane.org>
À: MQSERIES-0lvw86wZMd9k/bWDasg6f+***@public.gmane.org
Envoyé: Lundi 14 Juillet 2014 19:43:28
Objet: Re: Qalias attributes

I just did a quick test with a trace where the alias queue had a DEFPSIST(YES) which pointed to a target base queue whose DEFPSIST(NO) and ran the amqsput/amqsbcg samples on it. The message came out as persistent. So looks like the qalias DEFPSIST attribute took precedence.

Thanks,

Tim

From: MQSeries List [mailto:MQSERIES-0lvw86wZMd9k/bWDasg6f+***@public.gmane.org] On Behalf Of Sailesh Krishnamurti (BLOOMBERG/ 120 PARK)
Sent: Monday, July 14, 2014 12:28 PM
To: MQSERIES-0lvw86wZMd9k/bWDasg6f+***@public.gmane.org
Subject: Re: Qalias attributes

I believe the base Queue attribute takes precedence and a log entry is written in the Qmgr AMQERR log.

----- Original Message -----
From: MQSERIES-0lvw86wZMd9k/bWDasg6f+***@public.gmane.org
To: MQSERIES-0lvw86wZMd9k/bWDasg6f+***@public.gmane.org
At: Jul 14 2014 13:27:07

've been searching but can't find that IBM has documented this:

If a queue has an alias entry that is used for access and the two have different attributes, e.g. persistent, which takes precedence?

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Bob Juch

2014-07-14 19:01:40 UTC

Permalink

Tim,

Thanks for taking time to test!

Bob Juch

Post by Tim Zielke
I just did a quick test with a trace where the alias queue had a
DEFPSIST(YES) which pointed to a target base queue whose DEFPSIST(NO) and
ran the amqsput/amqsbcg samples on it. The message came out as persistent.
So looks like the qalias DEFPSIST attribute took precedence.
Thanks,
Tim
Behalf Of *Sailesh Krishnamurti (BLOOMBERG/ 120 PARK)
*Sent:* Monday, July 14, 2014 12:28 PM
*Subject:* Re: Qalias attributes
I believe the base Queue attribute takes precedence and a log entry is
written in the Qmgr AMQERR log.
----- Original Message -----
At: Jul 14 2014 13:27:07
If a queue has an alias entry that is used for access and the two have
different attributes, e.g. persistent, which takes precedence?
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Tim Zielke

2014-07-14 19:16:19 UTC

Permalink

No problem! It only took a few minutes to do, since I used the MH06 supportpac to review the trace. :-)

Thanks,
Tim

From: MQSeries List [mailto:***@LISTSERV.MEDUNIWIEN.AC.AT] On Behalf Of Bob Juch
Sent: Monday, July 14, 2014 2:02 PM
To: ***@LISTSERV.MEDUNIWIEN.AC.AT
Subject: Re: Qalias attributes

Tim,

Thanks for taking time to test!

Bob Juch

On Mon, Jul 14, 2014 at 1:43 PM, Tim Zielke <***@aon.com<mailto:***@aon.com>> wrote:
I just did a quick test with a trace where the alias queue had a DEFPSIST(YES) which pointed to a target base queue whose DEFPSIST(NO) and ran the amqsput/amqsbcg samples on it. The message came out as persistent. So looks like the qalias DEFPSIST attribute took precedence.

Thanks,
Tim

From: MQSeries List [mailto:***@LISTSERV.MEDUNIWIEN.AC.AT<mailto:***@LISTSERV.MEDUNIWIEN.AC.AT>] On Behalf Of Sailesh Krishnamurti (BLOOMBERG/ 120 PARK)
Sent: Monday, July 14, 2014 12:28 PM
To: ***@LISTSERV.MEDUNIWIEN.AC.AT<mailto:***@LISTSERV.MEDUNIWIEN.AC.AT>
Subject: Re: Qalias attributes

I believe the base Queue attribute takes precedence and a log entry is written in the Qmgr AMQERR log.
----- Original Message -----
From: ***@LISTSERV.MEDUNIWIEN.AC.AT<mailto:***@LISTSERV.MEDUNIWIEN.AC.AT>
To: ***@LISTSERV.MEDUNIWIEN.AC.AT<mailto:***@LISTSERV.MEDUNIWIEN.AC.AT>
At: Jul 14 2014 13:27:07
've been searching but can't find that IBM has documented this:

If a queue has an alias entry that is used for access and the two have different attributes, e.g. persistent, which takes precedence?

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2014-07-14 22:00:15 UTC

Permalink

The Alias attributes always take precedence over the base queue to which
it points. This is true for default persistence, default priority, put
enabled/disabled, get enabled/disabled, etc. It's also true that
authorities granted to an Alias override authorities on the base queue.

Post by Bob Juch
If a queue has an alias entry that is used for access and the two have
different attributes, e.g. persistent, which takes precedence?
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Bob Juch

2014-07-14 22:41:21 UTC

Permalink

Thanks. My predecessor used an alias for EVERY queue with capricious
settings.

Bob Juch

Post by RW
The Alias attributes always take precedence over the base queue to which
it points. This is true for default persistence, default priority, put
enabled/disabled, get enabled/disabled, etc. It's also true that
authorities granted to an Alias override authorities on the base queue.
If a queue has an alias entry that is used for access and the two have
different attributes, e.g. persistent, which takes precedence?
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2014-07-14 23:50:51 UTC

Permalink

Bob,

It may actually be the case that such settings were not capricious, but
necessary to support some application architectural requirements. You
may need to check with your system designers to see if that's the case.

I always advocate the use of Alias queues as a way to isolate
applications from the actual underlying queues and to support
application portability.

Post by Bob Juch
Thanks. My predecessor used an alias for EVERY queue with capricious
settings.
Bob Juch
The Alias attributes always take precedence over the base queue to
which it points. This is true for default persistence, default
priority, put enabled/disabled, get enabled/disabled, etc. It's
also true that authorities granted to an Alias override
authorities on the base queue.

Post by Bob Juch
If a queue has an alias entry that is used for access and the two
have different attributes, e.g. persistent, which takes precedence?
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Bob Juch

2014-07-15 00:08:21 UTC

Permalink

WR, thanks but when there's a set of six queues for six different
application servers and two of the local queues have default persistence
and two of the aliases for different locals in the same set are persistent,
I choose to think it was just sloppy.I checked with the application folks
and there was no requirement for that.

I'm not going to change anything as the required testing isn't worth it.

Bob

Post by RW
Bob,
It may actually be the case that such settings were not capricious, but
necessary to support some application architectural requirements. You may
need to check with your system designers to see if that's the case.
I always advocate the use of Alias queues as a way to isolate applications
from the actual underlying queues and to support application portability.
Thanks. My predecessor used an alias for EVERY queue with capricious
settings.
Bob Juch

Post by RW
The Alias attributes always take precedence over the base queue to
which it points. This is true for default persistence, default priority,
put enabled/disabled, get enabled/disabled, etc. It's also true that
authorities granted to an Alias override authorities on the base queue.
If a queue has an alias entry that is used for access and the two have
different attributes, e.g. persistent, which takes precedence?
------------------------------
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Bruce Lerner

2014-07-15 14:28:36 UTC

Permalink

"The Alias attributes always take precedence over the base queue to which it points. This is true for default persistence, default priority, put enabled/disabled, get enabled/disabled, etc. It's also true that authorities granted to an Alias override authorities on the base queue."

Be careful here.

Generally, it is the object name that is MQOPENed that sets attribute values - WITH EXCEPTIONS, namely:

First, the persistence attribute at the queue (alias or otherwise) is NOT a default. If the application specifies that this message is persistent (or non-persistent), the queue attribute value is not relevant. If the application specifies 'use the persistence queue attribute value (PERSISTENCE_AS_Q_DEF), then the message will take on the value as set in the queue (alias) attribute.

PRIORITY_AS_Q_DEF behaves the same. If the app sets message priority to 8, the queue attribute is not relevant.

Lastly, if the base queue is PUT(DISABLED), the next MQPUT will fail. The alias definition PUT(ENABLED) does not override the base PUT attribute value.

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Bruce Lerner

2014-07-15 15:05:10 UTC

Permalink

"I believe the base Queue attribute takes precedence and a log entry is written in the Qmgr AMQERR log."

The base (target of the alias) queue attributes MAY or MAY NOT take precedence - it depends. Nothing is written to the error logs.

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Bruce Lerner

2014-07-15 16:55:21 UTC

Permalink

"...but when there's a set of six queues for six different application servers and two of the local queues have default persistence and two of the aliases for different locals in the same set are persistent, I choose to think it was just sloppy.I checked with the application folks and there was no requirement for that."

It's been my experience that developers and sysadmins misunderstand the persistence queue attribute.

Developers should set message persistence when building the message MQMD. There are three possible values the developer can specify, namely: this message is persistent, OR this message is non-persistent, OR this message should take on the persistence value set at the queue. If developers specify the last option, the message put to the queue will take on the DEFPSIST queue attribute value.

My personal opinion: I strongly oppose use of the last option (this message should take on the persistence value set at the queue) is that system admins can change this value in-flight; and it will be difficult or impossible to determine how and why message persistence was determined. Worst, non-persistent messages are not logged, and might be lost due to queue full, no DLQ, types of down-the-network issues.

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Bob Juch

2014-07-15 17:04:58 UTC

Permalink

Bruce,

I agree with you and write my own code that way. However almost no one else
does.

Since about 99% of all MQ messages that I have seen (and I know I haven't
seen everything) are request/response messages where there's a person
waiting for the response, so the MQGET WAIT expires after a short time,
there's no point in having those messages persist.

Bob Juch

Post by Bruce Lerner
"...but when there's a set of six queues for six different application
servers and two of the local queues have default persistence and two of the
aliases for different locals in the same set are persistent, I choose to
think it was just sloppy.I checked with the application folks and there was
no requirement for that."
It's been my experience that developers and sysadmins misunderstand the
persistence queue attribute.
Developers should set message persistence when building the message MQMD.
There are three possible values the developer can specify, namely: this
message is persistent, OR this message is non-persistent, OR this message
should take on the persistence value set at the queue. If developers
specify the last option, the message put to the queue will take on the
DEFPSIST queue attribute value.
My personal opinion: I strongly oppose use of the last option (this
message should take on the persistence value set at the queue) is that
system admins can change this value in-flight; and it will be difficult or
impossible to determine how and why message persistence was determined.
Worst, non-persistent messages are not logged, and might be lost due to
queue full, no DLQ, types of down-the-network issues.
in the message body (not the subject), write: SIGNOFF MQSERIES
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