Maximum amount of memory (in Kbyte) to use for pattern matching. The maximum value is about 2000000. Use this to work without a limit. When Vim runs into the limit it gives an error message and mostly behaves like CTRL-C was typed. Running into the limit often means that the pattern is very inefficient or too complex. This may already happen with the pattern "(.)" works much better. Might also happen on redraw, when syntax rules try to match a complex text structure. Vim may run out of memory before hitting the 'maxmempattern' limit, in which case you get an "Out of memory" error instead.