QUICKSAM — Sequential file I/O manager

QUICKSAM is a component program product of QUICKSTART performs the duties of READing and WRITEing records of MVS sequential files. Such files are commonly referred to as BSAM, QSAM, or VSAM ESDS files. QUICKSAM supports Fixed length, Variable Length, Variable Blocked Spanned (API Mode only), and VSAM ESDS (API Mode only) records. It also supports Hiperbatch for input files.

By having QUICKSAM perform the sequential file operations on behalf of the application program, QUICKSAM is able to track the necessary positioning information throughout the execution of the application program. This enables QUICKSTART to successfully re-position the sequential file during an application program restart.

With Transparent Mode, QSFD is automatically invoked during normal COBOL I/O verb processing (e.g. READ, WRITE, OPEN CLOSE), which in turn issues requests to QUICKSAM.

With API Mode, if the COBOL I/O interception module QSFD is used, your COBOL applications can continue to use COBOL verbs for sequential file I/O as before. QSFD will intercept these verbs and perform CALLs to QUICKSAM “under the covers” to ensure repositionability for your sequential files.

As an alternative within API Mode, CALLs to QUICKSAM replace the COBOL verbs and constructs for sequential file I/O, such as “OPEN”, “CLOSE”, “READ” and “WRITE”. When used in IDEAL programs, calling QUICKSAM to perform READs from and WRITEs to sequential files also eliminates the need to use sequential DataViews.

Since module QUICKSAM is used in all modes, performance is the same.

An example of an API CALL to QUICKSAM is:

where MY-IO-AREA is the Working Storage variable into which the data record of the “READ” request is to be placed, or the data record from which a “WRITE” request to be extracted. SAM1-DEFINITION is a working storage area containing specific information about the sequential file, such as its DDNAME and I/O Request Type.