Run on a single-processor computer

If you are running the database server on a single-processor computer, set the MULTIPROCESSOR configuration parameter to 0. To run the database server with only one CPU virtual processor, set the SINGLE_CPU_VP parameter to 1.

Setting MULTIPROCESSOR to 0 enables the database server to bypass the locking that is required for multiple processes on a multiprocessor computer. For information about the MULTIPROCESSOR configuration parameter, see the HCL® Informix® Administrator's Reference.

Setting SINGLE_CPU_VP to 1 allows the database server to bypass some of the mutex calls that it normally makes when it runs multiple CPU virtual processors. For information about setting the SINGLE_CPU_VP parameter, see the HCL® Informix® Administrator's Reference.
Important: Setting VPCLASS num to 1 and SINGLE_CPU_VP to 0 does not reduce the number of mutex calls, even though the database server starts only one CPU virtual processor. You must set SINGLE_CPU_VP to 1 to reduce the amount of latching that is performed when you run a single CPU virtual processor.
Setting the SINGLE_CPU_VP parameter to 1 imposes two important restrictions on the database server, as follows:
  • Only one CPU virtual processor is allowed.

    You cannot add CPU virtual processors while the database server is in online mode.

  • No user-defined classes are allowed. (However, users can still define routines that run directly on the CPU VP.)

For more information, see Add virtual processors in online mode.