The following must be observed:
Uniprocessor performance
When migration is to take place from a /390 server (uniprocessor) to an x86 server (multiprocessor), the total RPF value can remain unchanged, but the uniprocessor performance will be lower in most cases. This must, for example, be taken into account for batch applications which cannot be operated in parallel.CPU performance: TU portion
The CISC firmware ensures that customer applications execute unchanged on x86 servers. The RPF value of the server with x86 architecture applies for a TU portion of 40 to 50% of the entire CPU requirement. When the TU portion is 50% or higher, an additional performance requirement of approx. 10% should be provided for the new x86 server.Peripherals: networking
The integrated LAN controllers of the server with x86 architecture are available. An HNC is not required, nor can it be used.Memory requirements
As a rule the standard main memory configuration of the x86 servers is sufficient. For the exceptions see section "Special features for x86 servers".Object format
System exit routines must be cleaned up and recompiled, see the "Migration Guide" [17 (Related publications)].
Example: calculating the RPF value for a target x86 server
The following assumptions apply for the /390 servers used to date:
S175-10C (300 RPF)
Load: OLTP mode (UTM/SESAM)
CPU workload 80% (50% of that TU)
BS2000/OSD V9.0
Growth requirements15%
This results in the following calculation for the target x86 server:
300 RPF * 1.1 (higher performance requirement because of TU portion 50%) * 1.04 (migration from BS2000 V9.0 to V11.0) = 344 RPF
In order to keep the workload to the 65% recommended for TP mode despite the growth:
344 RPF * 1.2 (target workload 65%) * 1.15 (growth requirements) = 475 RPF
Th x86 server with the next higher RPF level is an SE300-30F server with 520 RPF and therefore would be suitable.
The switch from a uniprocessor to a multiprocessor with three CPUs must be borne in mind here which may effect the batch runtimes.
In rare cases application-dependent special influences can reduce the CPU performance, e.g.:
Intensive use of decimal, floating point or EX commands
Self-modifying code
Mixed code and data on the same memory page
Alignment violations
Very frequent SVC calls