How to simulate postgresql recovery mode?

I would like to simulate putting postgresql into "recovery mode". Few times i have situation where postgresql puted himself into recovery mode. In logs i had: Oct 18 06:37:35 xx postgres: [19-1] 2014-10-18 06:37:35.441 CEST|5738|xx|yy|FATAL: the database system is in recovery mode It was caused by oom which killed one of process. But when i try to simulate it in test environment - postgresql restarts. How to prevent postgresql from restart and let him stay in recovery mode?