The system log in SM21 shows errors as follows for user SAPSYS:
Operating system call connect failed (error no. 150 )
The messages in the syslog: Q0 I Operating system call connect failed (error no. 150 )
usually correspond to the following messages in the SPO WP trace files:
M ***LOG Q0I=> NiBufIConnect: connection pending after 10240ms: connect (150: Operation now in progress) [nibuf.cpp 4658] M *** ERROR => NiBufIConnect: non-buffered connect pending after 10240ms (hdl 38;126.96.36.199:515) [nibuf.cpp 4669]
If that is the case, these kinds of errors can occur if you try to print directly to printers, rather than through a spool server as is recommended. SAP does not recommend connecting network printers directly, as described in note 64628:
# 64628 - Using network printers from R/3
Some printers cannot buffer enough data and simultaneously handle further connection requests from the network. As per Note # 64628, you should ensure there is a print server between SAP and the printer.