11.4 Keeping Heavily Used Files Open

The LANSA OPEN command can be used to keep file(s) open until a specific CLOSE command is issued against them.

For instance, imagine a small order processing system that could be visualized like this:

                          ORDWRK

                            |

                     -------|-------

                    |       |       |

                  ORD001  ORD002  ORD003

 

When a user enters this system and begins jumping from ORD001 to ORD002 to ORD003, and so on, a fair amount of computer resource can be wasted opening and closing files used by all the functions.

For instance, all 3 functions might use files TABLES (system tables), ORDHDR (order header details) and ORDLIN (order line details).

Thus when the user exits from ORD001 all 3 files are closed. When the user invokes ORD002, all 3 files are opened again. This continual opening and closing is a waste of computer resource and degrades response times.

To fix this problem we might code a "file opener" called ORD004 that looked like this:

  OPEN FILE(TABLES) USE_OPTION(*KEEPOPEN)

  OPEN FILE(ORDHDR) USE_OPTION(*KEEPOPEN)

  OPEN FILE(ORDLIN) USE_OPTION(*KEEPOPEN)

  CALL PROCESS(ORDWRK)

which would fit into the existing system like this:

                             ORD004

                                |

                                |

                             ORDWRK

                                |

                         -------|-------

                        |       |       |

                      ORD001  ORD002  ORD003

 

In this situation, the implicit OPEN and CLOSE requests issued by ORD001, ORD002 and ORD003 are ignored, which results in much faster processing.