IBM Parallel Sysplex - Server Time Protocol (STP)

Server Time Protocol (STP)

Maintaining accurate time is important in computer systems. For example, in a transaction-processing system the recovery process reconstructs the transaction data from log files. If time stamps are used for transaction-data logging, and the time stamps of two related transactions are transposed from the actual sequence, then the reconstruction of the transaction database may not match the state before the recovery process. Server Time Protocol (STP) can be used to provide a single time source between multiple servers. Based on Network Time Protocol concepts, one of the System z servers is designated by the HMC as the primary time source (Stratum 1). It then sends timing signals to the Stratum 2 servers through use of coupling links. The Stratum 2 servers in turn send timing signals to the Stratum 3 servers. To provide availability, one of the servers can be designated as a backup time source, and a third sever can be designated as an “Arbiter” to assist the Backup Time Server in determining if it should take the role of the Primary during exception conditions.

STP has been available on System z servers since 2005.

More information on STP is available in “Server Time Protocol Planning Guide”