Chapter 1. IBM Enterprise Workload Manager overview 15
and can be provided to Load Balancers to manage workload at the edge servers. Eventually,
as EWLM evolves, this data will also be used to manage the entire domain.
1.3 Interaction with existing workload management
The following sections summarize the relationships between EWLM and the existing
workload management capabilities available on the zseries and pSeries platform, how they
interact, and how and when you can use these functions.
1.3.1 Workload management on zSeries
As shown in Figure 1-8, EWLM and z/OS WLM policy structures are conceptually the same.
The main difference is related to the work managers and to the logical components that
receive and submit the work requests. As work managers, EWLM supports applications and
z/OS WLM platforms, and zWLM supports several subsystems, including CB, CICS®, DDF,
and IMS™.
Figure 1-8 EWLM and z/OS WLM comparison
To associate a work request to a service class, a work manager passes some attribute values
that EWLM matches against filters and z/OS WLM matches against subsystem work
qualifiers. This process is called
classification.
The attribute values for work requests received by the entry application of an EWLM
Management Domain might be different from those passed to z/OS WLM, especially if the
classification on the distributed platform happened in an application environment different
from the entry point on z/OS. For this reason it may not always be possible to have a
one-to-one mapping for EWLM service classes and z/OS WLM service classes.
EWLM and z/OS WLM Policy
EWLM
Domain Policy
Service Policy
Workloads
Service Classes
Applications
Transaction Classes
Filters
Platforms
Process Classes
Filters
Partitions
Partition Classes
Filters
z/OS WLM
Service Definition
Service Policy
Workloads
Service Classes
Subsystem Classification rules
- Work qualifiers
Report Classes
Application Environments
Scheduling Environments
Options
16 IBM Enterprise Workload Manager V2.1
ARM enablement on z/OS
Workload Manager on z/OS has provided workload management services to middleware
such as DB2, WebSphere, CICS, and IMS for a long time. For example, DB2 DIST uses
WLM enclave services to schedule and process received work requests. In the current
implementation, EWLM on z/OS leverages the existing WLM services and maps them to
ARM calls, so that an EWLM managed server can simply pick up the performance data and
send it to the domain manager. Figure 1-9 depicts a general flow.
Figure 1-9 ARM and enclave
When the EWLM address space is started it connects to WLM. Its main functions are:
򐂰 Manage the EWLM policy received from the domain manager.
򐂰 Collect the performance data and send it to the domain manager.
When DB2 is started it connects to WLM and specifies that it will participate in EWLM. The
DB2 DIST address space is then registered to ARM on z/OS as an EWLM application
participant.
ARM data is captured only if a correlator is sent in from an ARM-enabled distributed
application such as WebSphere; otherwise, DB2 continues processing distributed requests
as it usually does.
When DB2 receives the correlator from a distributed application, DB2 DDF creates an
enclave and starts a work request. Attribute values such as PLAN, PACKAGE, and
CONNECTION are passed with the correlator to zWLM to classify the work request and
associate it to a service class.
When an enclave is created by DDF, an arm_start_transaction is implicitly invoked to mark
the beginning of a transaction, and then an arm_stop_transaction gets called at the end of
processing a database request message. A pair of start and stop transaction is associated
with each database request message from a distributed application or DRDA® requester until
a commit is received and the enclave is then deleted.
EWLMMS address space
EWLM_connect
Policy management
Collect data
Send data to Control
Center
EWLM_disconnect
ARM and Enclave Transactions
DB2 DDF
- DB2DIST address space
Connect to WLM
(IWNCONN)
arm_register_application
arm_start_application
arm_register_transaction
Create enclave (IWMECREA)
Enclave workrequest start and
stop calls (
IWMESTRT, IWMESTOP
)
arm_start_transaction
arm_stop_transaction
arm_start_transaction
arm_stop_transaction
arm_start_transaction
arm_stop_transaction
Enclave delete
(IWMEDELE)
Disconnect from WLM
arm_stop_application
arm_destry_application
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