OSI/MHS Configuration and Management Manual

Sizing and Tuning Your OSI/MHS Subsystem
OSI/MHS Configuration and Management Manual—424827-003
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MR Group Attributes
major sync occurs. The checkpoint size multiplied by the window size multiplied by 1K
equals the amount of recovered data in retry transmission after a connection
interruption.
The WINDOW-SIZE and CHECKPOINT-SIZE attributes affect the amount of memory
demand by an RTS process. For example, if the window size is 30 and the checkpoint
size is 30, the maximum amount of memory required for a series of requests to OSI/AS
is 30 x 30 x 1K (900K). Insufficient memory can cause resource shortage event
messages, and incoming associations are likely to be rejected with a reason code
denoting that the RTS process is busy.
Recovery
The SAFE-STORE-WINDOW attribute specifies how many data packets are sent
before recovery information is written to disk. A large value increases memory
demand, while a small one increases the number of disk accesses. Specifying 0
prevents recovery information from being written; this setting makes normal processing
faster, but it makes association recovery slower.
CUG Checking
The CUG-CHECK attribute can dramatically affect performance, because the
verification performed during routing can involve many reads of the CUG database.
Route and Link Retry
Route and link-retry attributes affect performance by controlling the frequency of
association establishment attempts. A large number of failed association attempts
creates significant overhead in lower layers and network services.
The description of the ENTRY object in Section 2, Management Environment for
OSI/MHS, describes the link and route-retry attributes. You can alter these attributes
online. For more information about them, see the OSI/MHS SCF Reference Manual.
MR Group Attributes
The best relative locations of MR, RTS, and OSI/AS processes is difficult to predict. It
can sometimes improve performance to run an MR group, or the RTS process
specifically, in the same CPU as the OSI/AS process that serves it. This configuration
eliminates data traffic between CPUs. However, the benefit can be offset by the fact
that the processes share the CPU and cannot run in parallel.
MS Class Attributes
Adjusting the number of mailboxes per message store affects the size of PDU stores
and SQL databases. The more users a single MS group is serving, the more
opportunity there is for bottlenecks in MS access. The mailbox save and restore
utilities, described in Appendix C, Mailbox Save and Restore Utilities, provide a way of