SAP PO – temporarily out of MPI buffers -> roll out

In logs You can find information like below:

[Thr 140662462117632] *** WARNING => IcmReadFromConn(id=18/908078): temporarily out of MPI buffers -> roll out [icxxthrio.c 3429][Thr 140662823061248] *** WARNING => IcmReadFromConn(id=9/908079): temporarily out of MPI buffers -> roll out [icxxthrio.c 3429]

The MPI buffer usage depends on the number of open HTTP connections and the number/size of HTTP messages being processed by the server.
The ICM requires two memory pipes (MPI) for each HTTP connection. You need to adjust parameter like icm/max_conn. The default value is 2000.

Read more about limits for icm/max_conn in note: 2007212 – Tuning SAP Web Dispatcher and ICM for high load.

More detailed information regarding MPI parameters settings can be found at ICM and Web dispatcher: MPI parameters settings