1、Amendment 2:1999 to National Standard of Canada CAN/CSA-2243.181-89 Amendment 21993 to International Standard IS0 8571-21988 has been adopted without modification as Amendment 21999 to CAN/CSA-Z243.181-89. This Amendment was reviewed by the CSA Technical Committee on Information Technology (TCIT) un
2、der the jurisdiction of the Strategic Steering Committee on Information Technology and deemed acceptable for use in Canada. July 1999 Information processing systems - Open Systems Interconnection - File Transfer, Access and Management - Part 2 : Virtual Filestore Definition AMENDMENT 2 : Overlapped
3、access (Reaffirmed 2004) Systemes de traitement de /information - lnterconnexion de systemes ouverts - Transfert, acces et gestion de fichiers - Partie 2: Definition du systeme de fichiers virtuel AMENDEMENT 2 : Chevauchement dacces Reference number IS0 857 1 -2:1988/Amd.2:1993 (E) IS0 8571-2:1988/A
4、rnd.2:1993 (E) Foreword IS0 (the International Organization for Standardization) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of IS0 or IEC participate in the development of International Standards
5、 through technical committees established by the respective organization to deal with particular fields of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non- governmental, in liaison with IS0 and IEC
6、, also take part in the work. In the field of information technology, IS0 and IEC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard
7、 requires approval by at least 75 % of the national bodies casting a vote. Amendment 2 to International Standard IS0 8571-2:1988 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology. IS0 8571 consists of the following parts, under the general title Information processing s
8、ystems - Open Systems Interconnection - File Transfer, Access and Management: - Part 7 : General introduction - Part 2 : Virtual Filestore Definition - Part 3 : File Service Definition - Part 4 : File Protocol Specification - Part 5 : Protocol Implementation Conformance Statement Proforma 0 ISOAEC 1
9、993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. ISOAEC Copyright Office Case postale 56 CH-1211 Geneve 20 Switzerland IS0
10、8571-2:1988/Amd.2:1993 (E) Information processing systems - Open Systems Interconnection - File Transfer, Access and Management - Part 2 : Virtual Filestore Definition AMENDMENT 2 : Overlapped access 0 Introduction Clause 0 provides an introduction to this amendment The text in this clause is not in
11、tended for inclusion in IS0 8571 part 2- 0.1 General IS0 8571 part 2 defines an abstract model of the virtual filestore for describing files and filestores. Sets of actions are defined that may be used to manipulate the elements of this model, and the properties of individual files and associations
12、are defined in terms of attributes. Thii amendment extends these definitions to incorporate the concepts of overlapped access. 09 Rationale The objective in introducing overlapped access is to allow more efficient accss to structured files when a single initiator has a need to perform many reading a
13、nd updating operations; the serial nature of the current FTAM data transfer services introduces a significant control overhead if the FADUS are small. In this context. an FADU is small if its transmission time is comparable with the time to complete a confirmed service on the association (the associ
14、ations round trip delay). 0.3 Summary The current design envelope that there should be at most one file selection per association and one file open per file selection is maintained. If access to more than one file is to be overlapped, more than one association is necessary, The overlapped access tak
15、es place within a constant set of presentation contexts established as at present when the file is opened, or previously. Two different degrees of overlap have been identified. Firstly, requests for future accBssBs may be issued whilst a previously requested BDT action is in progress, allowing the c
16、reation of a queue of read and write requests. In general, PCI relating to a given BDT action may be overlapped with other BDT adions. subject to restrictions; this is called co- overhp. Secondly, read and write actions can be performed in parallel, so tM both directions of data transfer am exploite
17、d at any one time. Requests are then taken from the queue whenever either diredion of transfer becomes free. This is called concurrent access. The transfer of a single FADU, Specai in a single FREAD request has the same interpretation as In IS0 8571. The resultant effed on the virtual filestore of a
18、 set of overlapped requests using consecutive access shall be the same as that of the equivalent set of requests issued In series; the service provided is serialii. If concurrent access is used then the resultant effed of a set of write actions on the virtual fiiestore, is also serialii. However, du
19、e to the nondeterrninism Introduced by the use of concurrent access, it is also possible that in some uses of the service, the data transferred as a result of a read action is not consistent with the current state of the file. 1 Scope and field of application This amendment makes no additions to cla
20、use 1. 2 References This amendment makes no adfitions to clause 2. 3 Reference model definitions This amendment makes no additions to clause 3. 4 Service conventions definitions This amendment makes no additions to clause 4. 5 FTAM Definitions This amendment makes no &itions to clause 5. 1 IS0 8571
21、-2:1988/Arnd.2:1993 (E) Section one: The filestore model 6 File selection 8 Actions on files This amendment makes no additions to clause 6. 7 File structures 7.6 Identification structure Add last paragrzph: If concurrent access is in use then the current locations for read and write actions are inde
22、pendent. The semantics of the FADU identifirs previous, current and next, are dependent on the action to be performed. If concurrent accessif h usethen theeffects of aset of read actions, and of a sat of write actions, are independently serializable. However. the data transferred as a result of a ma
23、d adon may not be consistent with the current state of the file in some situations. This ame-nt makes no aolditons to clause 9. 2 IS0 857 1 -2:1988/Amd.2:1993 (E) Section two: Actions on the Filestore 10 Actions on complete files lB13 amendment makes no additions to clause 10. 11 Actions for file ac
24、cess 11.1 Locate Insert second pagqoh If concurrent access is in use then separate FADUS may be located for read and wrie operations. 11.6 Erase Insert second mrzph If concurrent access is in use then the operation may be used to erase the FADU currently located for either read or wrie operations. N
25、OTE - In anarnent access, il either the read or mite MBnt kcation is not within the erased FADU then that locaoion remains UElffected. 3 IS0 857 1 -2:1988/Amd.2:1993 (E) Section three: Attribute definitions 12 File attributes then the attribute contains two elements corresponding to the locations th
26、at &-e maintained for the read and write actions. Amend first sentence of third paragraph: The values of the elements may be either, . This amendment makes no additions to clause 12. 13 Activity attributes 13.4 Current Location lnsert clause and renumber: 13.6 Current degree of overlap The current d
27、egree of overlap attribute is a scalar attribute. It indicates the degree of overlapped access that is in use in the open regime. The value of the attribute is an integer. The degree of overlap attribute is the open regime- Amend firs1 sentence of first paragraph: The current location is a vector at
28、tribute that indicates the current position within the file. Insert as second paragraph: If concurrent access is not in use then the attribute only contains a single element. f concurrent access is in use Of the Table 4 - Activity attributes Attribute Current access request Current initiator identit
29、y Current location Current processing mode Current degree of overlap Current calling application entity title Current responding application entity title Current account Current concurrency control Current Wng style Current access passwords boolean vector GraphicString vector of Node-Descriptor-Data
30、-Element boolean vector integer application entity titie application entity title Graph iCStri ng vector of enumeration boolean GraphicString or OCTET STRING Minimum Attribute Range see note 9 to 8 characters see note see note see note No minimum required No minimum required 1 to 8 characters see no
31、te No minimum required 0 to 8 characters or cctets 4 14 Attribute groups 14.1 Kernel group Insert in 6) and renumber: 6) arrent degree of overlap IS0 8571-2:1988/Amd.2:1993 (E) 15 Minimum attribute ranges Replace table 4. 5 IS0 857 1-2: 1988/Arnd.2:1993 (E) UDC 681.3 : 621.39 Descriptors: data proce
32、ssing, information interchange, network interconnection, open systems interconnection, communication procedure, files, transfer, access, management. Organisme sons but lucratif du secteur priv6 A not-for-profit private sector organization 7 78, boulevard Rexdale 7 78 Rexdale Boulevard Toronto, Ontario Canada M9W 7 R3 (4 7 6) 747-4000 Bureaux regionaux a Regional offices in Vancouver, Edmonton, Montreal
