Browse Prior Art Database

Preserving Integrity of Input/Output Requests

IP.com Disclosure Number: IPCOM000084609D
Original Publication Date: 1975-Dec-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Page, HL: AUTHOR

Abstract

An input/output (I/O) control technique is described which ensures that valid I/O requests are not made invalid by modification subsequent to validation. This is accomplished by locking each channel program during the internal it is being used to perform an I/O operation, so as to prohibit accessing and modification of the I/O channel program during such internal.

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Preserving Integrity of Input/Output Requests

An input/output (I/O) control technique is described which ensures that valid I/O requests are not made invalid by modification subsequent to validation. This is accomplished by locking each channel program during the internal it is being used to perform an I/O operation, so as to prohibit accessing and modification of the I/O channel program during such internal.

This technique assumes the requirement to execute I/O commands which fetch data from or store data to data areas, which are validly defined and to which the requester has suitable authority. The commands and data area definitions making up each channel program are assumed to be contained in a program entity called an I/O request block (IORB). It is further assumed that, due to other performance requirements, the system lacks the ability to ensure that an IORB will not be modified during its performance of an I/O operation. It is also assumed that the machine architecture provides the capability to lock the space containing the IORB, such that only the holder of the lock may modify the contents of the IORB.

With these assumptions in mind, the first step in the technique is for a user program to create a lockable storage space and acquire the lock associated with such space. The IORB is then created using the usual machine computational operators (e.g., MOVE). Subsequently, the IORB is utilized as the operand of a DO I/O (DOIO) instruction.

The machine checks...