It was founded in 1974 and is used where there is need of processing large number of business transactions per second and to record them instantly in a database.These are also known as HP NONSTOP Systems (Including Hardware and Software) are designed to meet all the demanding requirements of online transaction processing (OLTP). These are designed specifically for OLTP.

OLTP is the processing of data related to business transaction & activities as they occur. The major feature of OLTP is to keep the database up to date all the times. The unique feature provided by tandem OLTP system is Fault Tolerance, which means to withstand faults. Thus, the databases managed by such systems are always up-to-date.

That is, critical applications must continue to run even when faults occur. This feature is heart of applications like Stock Market, Healthcare, and ATMs. Given the mission critical nature of these applications, they must stay up and running during the hours they are needed.


  • TNS – Based on CISC technology, a larger number of instruction set, numerous addressing modes, multiple m/c instructions and special purpose instructions.

  • TNS/R – Based on RISC technology, a small, simple instruction set, general purpose registers & a high performance instruction execution.


  • Availability – Make sure that the application is accessible to end users whenever they need.

  • Integrity – The processing results will be accurate.

  • Performance – It assures that the system will respond to request faster.



  • Fault Tolerance – running system 24X7X365.

  • Scalability – These are multi processor machines and more then 4000 processors can be added to increase the performance.

  • Data Integrity – Produces accurate results.

  • Performance – Meets expectations and does not delay business functions.


Tandem is developed using products such as PATHWAY, INSPECT, TMF and lot other subsystems like SPOOLCOM, MEDIACOM, NETBATCH, FUP, SCUP etc. Programming languages used are TAL, TACL, C, SCOBOL, COBOL85. Databases used are ENSCRIBE and NON STOP SQL (Embedded SQL).


  • Non Stop Kernel is the operating system for Non Stop Systems.

  • Non stop systems use dual ported device controllers that allow peripherals to be connected to two CPUs.

  • The primary keeps on sending the message “I am alive” as soon as this message is stopped the backup copy takes over.

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