In SRX platform, the factory default for the number of backup configurations allowed is five. Therefore, one can have one active configuration and upto five rollback configurations. Increasing this backup configuration number will result in increased memory usage on disk and increased commit time. SRX can increase this value to 50 configuration rollbacks by number through 0 to 49.
Once you set the command;
One can keep upto max of 50 config files. In order to enable rescue config, following command does the job.