This article provides information on how to obtain the session creation rate.
Output of the show security monitoring fpc <x> command:
root@SRX1400-A# run show security monitoring fpc 1 node1: ----------------------------------------------------------- FPC 1 PIC 0 CPU utilization : 0 % Memory utilization : 53 % Current flow session : 6024 Max flow session : 524288 Current CP session : 6223 Max CP session : 1048576 Session Creation Per Second (for last 96 seconds on average): 99 {primary:node0}[edit] root@SRX1400-A# run show snmp mib walk .1.3.6.1.4.1.2636.3.39.1.12.1.4.1.5 jnxJsNodeSessionCreationPerSecond.0 = 0 jnxJsNodeSessionCreationPerSecond.1 = 99