This INTEGER selects which configuration file slot, config1(1) or config2(2), the device's current running configuration is saved to; if no value is set, it saves to the booting configuration file instead. An admin sets this before or during a save operation to choose whether changes go to the primary or secondary config slot, which matters because this action writes all configuration including user accounts and AAA settings. Setting it to config2(2) saves the running config to the secondary slot, preserving config1 as a rollback copy.