Logon Groups:
Logon
groups (or work groups) are configured to dynamically distribute the load being
processed by the dialog work processes.
In
many cases, SAP systems will have 2 or more sap abap instances. In these cases,
logon groups can be configured to achieve dynamic distribution of dialog users
on the ABAP instances.
Setting
up logon groups helps in uniform distribution of the work load across the
available instances. While logging on using a logon group, the ABAP message
server is contacted to identify the instance with best performance statistics
within the selected logon group. A report runs in SAP every 5minutes which determines
the load across each server and updates in the memory area of the message
server. This information will be used by SAP GUI to determine the best instance
to distribute the next user.
SPACE is the default logon group.
By default, every instance of an SAP system (including central instance) is
assigned to the logon group SPACE. This performs uniform distribution of the
dialog workload.
However,
if you want to distribute users on some other criteria as following, you can create
additional logon groups using SMLG
transaction code.
Other
criteria:
Logon groups according
to SAP application / module: Separate logon groups can be
setup for applications/modules such as HR, FI/CO, SD, MM etc. It means HR
module users will be restricted to logon to identified instances, similarly
other module users are allowed to login to their respective identified
instances. The advantages of this method,
is only the programs of the respective module are loaded into the program buffer
of the particular instances of that logon group. Due to this, program buffer
requires less memory and this helps to avoid buffer displacements thus
improving system performance.
Logon groups according to language, country or company
division:
If your SAP system is operating across
multiple countries or languages, in that case it is good idea to create logon
groups specific to a country or language. By this way the data and text related
to specific country or language will be loaded into the buffers of the
respective instances.
This
minimizes buffer displacements and improves system performance. Also less
memory is required for the table buffer.
Logon groups for certain user groups:
i)
We
can setup separate logon groups for some department like sales whose work is
performance critical. For that logon groups we assign instances which operates with high level of
performance (e.g: high speed processors, less users per server, no background
or update workprocesses configured or a dedicated network etc)
ii)
Some
department users may take time-consuming reports in dialog mode. For these type
of users, you may have to create separate logon group and assign an sap
instance where profile parameter rdisp/max_wprun_time is set to very high
In
this way we can separate performance critical/resource intensive applications
from others.
Logon groups for
the SAP Web Dispatcher:
For direct ABAP web service requests, we
can setup logon groups that the SAP Web Dispatcher can use. If logon groups are
not configured for web dispatcher, the load is distributed to all ABAP instances
on which ICM is configured. Also, based
on URLs we can distribute certain group of requests to dedicated logon groups.
Logon groups for
ALE/RFC:
Asynchronous
RFCs are used to process in parallel. However if the parallel processes are not
limited properly, they can occupy all the available processes which impacts
dialog users and can bring down the application. So, it is good idea to create
separate logon groups for incoming RFC calls so that RFCs are kept separate
from workprocesses of online users and thus avoids impact to dialog users.
Guide lines:
After
assigning instances to logon groups
- We
need to verify whether the instances of logon groups are evenly distributed or
not
- If
an instance hangs or temporarily got disconnected, you should be able to
redistribute the users. So,
you need to setup at least 2 sap instances for each logon group.
- Setting
up logon groups involves extra administration and monitoring. So, unnecessarily
large number of logon groups shouldn’t be setup
How to setup logon groups?
SMLG transaction
code is used for creating logon groups.
Logon
to SAP system and goto SMLG transaction as shown below:
In the above example there are 2 instances
(00 and 09) in this SAP system. These are not yet assigned to any logon group.
We can
create a new logon group by clicking on highlighted create icon on the above
screen. It results in below screen.
In the
above screen, either select logon group from dropdown or provide its name if
you are newly creating. After that assign instance for that logon group and
click on copy to save the assignment.
In
this example iam creating two logon groups hr and fico and assigning instances
00 and 09 respectively. Please find below screenshots which explains the same.
Repeat
the same step and create logon group fico and assign instance 09 for it as
shown above.
After
doing this, you can see following logon groups in SMLG
Once
you are done with logon group setup, please log off from SAP system and goto
SAPGUI of the respective SAP system.
Click
on properties of the respective GUI entry and goto to connection tab as shown
below.
Please
select Group/Server selection option from the drop down of Connection Type as
shown above and maintain description and system id of the instance as shown
above.
Now,
you should be able to view the newly created logon groups as shown in below
figure:
Also, please note you are able to view logon
group SPACE also which gets created by default
Now,
you can configure any desired logon group to the users as shown below:
For
example in the above screen fico group is assigned to the end users in his GUI
so that now onwards, he will login into instance number 09 only.
How to delete logon group or
assignment?
If
you no longer require any logon group, you can delete by proceeding as shown
below:
i)Goto
SMLG transaction
ii)
Select the respective row and click on delete assignment which deletes the
assignment of an instance to a logon group (highlighted in green color in below
screen)
Click
on delete icon above which confirms deletion of assignment
iii)If
you wish to delete logon group itself, then select the respective logon group
and click on “delete group” in the above screen highlighted in red color (please
refer screen 1 of point ii above). This deletes the logon group itself and
removes all assignments related to this group.
How to check logon load
distribution in SAP?
Goto
transaction code SMLG as shown below and click on highlighted icon below to
view the load distribution across instances
Alternatively, you can view this by
navigating to Goto -> Load Distribution or by pressing F5 key in the
above screen
