IO Read Cancellation

9.6

This runtime now provides a method that allows a user to abort an AFILE, FILE, or IFILE READ that is taking an excessively long time before finding a record when using a FILTER. By default, the runtimes do not allow a READ to be aborted. This ability to abort a READ can be enabled using a new keyword named PLB_IOCANCELCHAR keyword in a runtime INI file or by using the SETMODE *IOCANCELCHAR instruction.

 

If a READ is aborted by using the cancel character or key, the OVER flag is set. A GETFILE using the IOCANCELFLAG keyword that retrieves the cancel flag that indicates whether the READ was aborted. Also, note that there are keywords for the OPEN and PREPARE instructions that can allow individual AFILE, FILE, and IFILE variables to invoke the use of the cancel character support.

Note:

  1. The cancel support must be enabled before the OPEN/PREP action of an AFILE, FILE, or IFILE variable. When the file is opened or prepared, the current cancel support is enabled Changing the runtime setting after a file is opened does not change the cancel support being used.

  2. The CHAIN instruction resets to current program cancel character value back to the default setting specified by the PLB_AAMCANCELCHAR INI keyword.

  3. When a FILTER is being applied to a file variable, the IO Cancel support affects the file variable read operations.

 

 

See Also: Disk I/O Instructions

 


PL/B Language Reference