Does anyone know what causes this error and how to fix it? It's a very long simulation.

When run in interactive mode all simulation data is stored in RAM, only when a write instruction is executed the data is saved to file. To prevent ngspice taking too much RAM and killing your machine a size limit is enforced. If 95% or system RAM is taken this warning is printed (and soon later process killed). You have two options 1. save less nodes to reduce storage size 2. use batch mode ngspice. In batch mode data is not kept in memory, it is saved immediately to disk in the raw file.

How can I to use mode batch ?

see the ngspic user manual:

ngspice -b -r rawfile.raw -o ngspice.out circuit.spice

schem has the batch mode option available in

SImulation->Configure simulators and tools

. In batch mode you lose all functionality in .control / .endc you can only do a

.tran ....

or .

dc ...

Ohh, thanks