This topic describes WebSphere MQ functions that are not supported
by a service integration bus
WebSphere MQ functions not available
There
are various functions available in a WebSphere MQ network that are not available
on a service integration bus that has a WebSphere MQ link or a WebSphere MQ client link. The
following list helps you identify those functions but it is given as guidance
rather than a complete definition. Functions not supported include:
- Native MQ client (this includes client applications that make use of the
base MQ classes for Java) attach.
- Message segmentation.
- Message grouping.
- The MQMD Offset. Original length, MsgFlags, MsgSeqNumber, and GroupId
fields are not supported because Message grouping and message segmentation
are not supported.
- Distribution lists.
- Reference messages.
- Triggering.
- Alternate user authority.
- Pass/set identity context.
- In a program, setting the attributes of a queue (that is, the equivalent
function of MQSET).
- Confirmation of arrival/delivery.
- Cluster sender/receiver channels (and cluster workload exits), because
a messaging engine cannot participate in a WebSphere MQ cluster.
- Server and requestor channels.
- API crossing exits.
- Data conversion exits.
- Channel exits.
- The equivalent to the MCAUSER and PUTAUTH fields of a channel.
- Networks based on NetBIOS, SPX or SNA.
- Message based command server.
- PCF (Programmable Canonical Form messages).
- Model queues. Service integration does not allow you to define model queues
of a given name. Service integration technology supports only one model queue
called the SYSTEM.DEFAULT.MODEL.QUEUE.
- Dynamic queue name prefix length. Service integration all dynamic queue
names with '_Q' and suffixes them with a unique id. This restricts the name
specified in the dynamic queue name field of the Object Descriptor to up to
12 chars. If this name is greater than 12 characters, then it is truncated
to 12 characters. In service integration, it is not possible to create a dynamic
queue with the full name specified in the dynamic queue name field of the
Object Descriptor.
- Mark skip backout option.
- Signal option on a get request.
- Version 3 get message options structures.
- All queue properties (the properties of a service integration destination
do not map, one for one, to the properties of a WebSphere MQ local queue,
for example).
- Poisoned messages. Service integration bus local destination definitions
have a maximum failed deliveries count (that is, the equivalent to the WebSphere
MQ BackoutThreshold value) but there is no equivalent of the WebSphere MQ
backout requeue queue name. In service integration technology, poisoned messages
are instead backed out to an exception destination. Additionally, in service
integration technology, when the number of times an application backs out
a poisoned message is equal to the maximum failed deliveries count, the message
is automatically backed out to an ExceptionDestination. If there is more
than one message in the current unit of recovery, only the poisoned message
is backed out to the ExceptionDestination. The remainder of the messages in
the unit of recovery are backed out to the destination from which they were
read.
- A strict limitation of 48 bytes on the name of a queue. Service integration
bus destination names can be greater than 48 bytes in length. If a destination
name is to be returned to a WebSphere MQ JMS application, then it is important
to use 48 byte destination lengths. Though, in some cases, it may be feasible
to define an alias destination with a name length of up to 48 bytes) to map
to a local destination with a name of length greater than 48 bytes.
Differences from WebSphere MQ delivery options
While
WebSphere MQ supports persistent and nonpersistent messages,
service integration supports five delivery options (also known as qualities
of service (QoS).
- BEST_EFFORT_NONPERSISTENT
- RELIABLE_NONPERSISTENT
- EXPRESS_NONPERSISTENT
- RELIABLE_PERSISTENT
- ASSURED_PERSISTENT
Outbound BEST_EFFORT_NONPERSISTENT, RELIABLE_NONPERSISTENT, and EXPRESS_NONPERSISTENT
messages sent to a WebSphere MQ network, are sent as nonpersistent messages
in the WebSphere MQ network. Outbound RELIABLE_PERSISTENT and ASSURED_PERSISTENT
messages, when sent to a WebSphere MQ network, are sent as persistent messages.
For
inbound messages from a WebSphere MQ network, the inbound nonpersistent reliability
(with possible values of BEST_EFFORT_NONPERSISTENT, RELIABLE_NONPERSISTENT,
and EXPRESS_NONPERSISTENT) and the inbound persistent reliability (with
possible values of RELIABLE_PERSISTENT and ASSURED_PERSISTENT), fields of
the MQLinkReceiver channel can be set to specify the service integration delivery
options to be used for nonpersistent and persistent messages.
Similarly,
for inbound messages from WebSphere MQ JMS clients, the inbound nonpersistent
reliability and the inbound persistent reliability fields of the MQ client
link can be set to control the message persistence.