Download PDF - IBM Redbooks

– HiperSockets local and virtual LAN connections to the database server and SCS
instances on z/OS
These connections use at least two CHPIDs (HiperSockets LANs) to separate
production from nonproduction (up to 16 are allowed) communication.
An alternative to HiperSockets is classic LAN connections using OSA or OSD, but you
can lose the performance advantages of HiperSockets and place significant load onto
the OSA hardware.
– OSA communication hardware to connect to the company network
Use OSA-2 at a minimum. OSA-3 and OSA-4 promise faster communication. The
speed is less critical for SAP user connections, but bandwidth and number of users
play a role. If you use OSA or OSD to connect to the SAP database server, a low
latency, high-bandwidth hardware is beneficial.
– For securing your external communication to the enterprise network, additional
hardware for firewalls and encryption (SAP recommended)
Preparing the z/VM host
SAP supports z/VM 6.1 and 6.2 as a managing host for Linux on System z application
servers. Try to use the latest SAP supported z/VM release when you plan a new installation or
platform renewal.
Similar to DB2 for z/OS, which incorporated many optimizations specific to SAP over the
years, z/VM is increasing the role of Linux on System z hosting, which increases the values
for SAP NetWeaver ASs. Consider the following best practices from the field:
► Create the LPAR, define the hardware resources, and install the z/VM software according
to the z/VM product documentation.
► Calculate and activate z/VM virtual memory, and allocate the paging space according to
the z/VM: CP Planning and Administration Manual, SC24-6803:
– Minimize paging and swapping. Define the Linux guests as small as possible without
having Linux swapping occur on a regular basis.
– Do not let Linux on System z perform paging. z/VM is more efficient than Linux on
System z if memory is overcommitted.
– Monitor Linux on System z paging, and let z/VM page as necessary.
– Configure some expanded storage for use by z/VM as a high-speed paging device.
(Memory of 2 GB does the job well.)
– Calculate DASD page space so that it does not exceed 50% utilization. Use the
following formula to calculate the page space:
Sum of all virtual guest sizes - (real memory + expanded memory) x 2
– Use multiple swap volumes to avoid I/O bottlenecks.
VM paging works best with large and continuous space on volumes of the same type.
Consider the 3390-A EAV DASD format, and consider dedicating them to the paging
job. Paging DASD must also use parallel FICON channels and the PAV storage access
feature to avoid bottlenecks. Striping is advised on a storage level.
► Turn off minidisk caching for swap minidisks on read-only minidisks.
The read ratio is not balanced by write path length.
Appendix B. Planning, preparing, and implementing the SAP landscape 185