Basis and others: Recommendation for using Precalculation Server

SAP recommends to use one Precalculation Server for one system. You can use the server for multiple systems if you observe no error on its usage.
Please use SAP BW Precalcualtion Service Multi-Instance ...

... with logon as This account:

Make sure that the "This account user" has full administrator rights. Do not run SAP BW Precalcualtion Service Multi-Instance with "Local system account"!

When using SAP BW Precalculation Service Multi-Instance it is mandatory to set RSADMIN parameter BWPREC_USE_NEW_LOAD = X as per note 1275837.
To set the parameter go into Tx SE38 and start the report SAP_RSADMIN_MAINTAIN.
The maximum number of instances to be created in case of MultiInstance is 3 (THREE). This is to avoid too much of load which may cause COM exceptions. You can create more if you experience no error on usage of 3 instances.
Despite the recommendation of using SAP BW Precalculation Service Multi-Instance, if you want to use the windows service SAP BW Precalcualtion Service, then use with "Local system account" and the option "Allow service to interact with desktop". Again, it is recommended to use SAP BW Precalcualtion Service Multi-Instance as it is more stable. If you want to use only one Precalculation Server Instance please use SAP BW Precalcualtion Service Multi-Instance and create only one Precalculation Server in Tx RSPRECADMIN - this way should be prefered instead using SAP BW Precalcualtion Service.
Start only one service at a time: SAP BW Precalcualtion Service Multi-Instance OR SAP BW Precalcualtion Service.
Make sure that select automatically option is set in all the broadcast setting. Special server should be used for testing purpose only. Using Special server can lead to failing of precalculation during mass precalculation.