Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Concurrent Operation of Two Channel Adapters

IP.com Disclosure Number: IPCOM000082727D
Original Publication Date: 1975-Jan-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 4 page(s) / 19K

Publishing Venue

IBM

Related People

Lindsay, RE: AUTHOR [+2]

Abstract

The IBM 3705 Communications Controller control program (NCP) -- at present does not provide support for the concurrent operation of two type 2 channel adapters. If one of the adapters -- called the "primary" -- is engaged in I/O operations, the other adapter -- called the "secondary" -- can only be used as a backup data path. That is, the secondary adapter can only accept a switch command to make it the primary adapter, in which case the old primary adapter becomes the new secondary.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 28% of the total text.

Page 1 of 4

Concurrent Operation of Two Channel Adapters

The IBM 3705 Communications Controller control program (NCP) -- at present does not provide support for the concurrent operation of two type 2 channel adapters. If one of the adapters -- called the "primary" -- is engaged in I/O operations, the other adapter -- called the "secondary" -- can only be used as a backup data path. That is, the secondary adapter can only accept a switch command to make it the primary adapter, in which case the old primary adapter becomes the new secondary.

In the case where only switched point-to-point communication lines or multipoint communication lines entirely controlled by one host are connected to the 3705, it is feasible to make both type 2 channel adapters capable of I/O operations at the same time, each adapter becoming a primary adapter. This means that the 3705 can service two independent host processors concurrently.

What follows is a description of those modifications to NCP which have been made to implement this feature. NCP Generation.

Generation of the network control program is accomplished in two stages by a series of jobs executed under OS/360. Stage one of NCP generation takes network control program generation macros -- Stage-one Macros -- and assembles them to form a sequential data set that becomes the stage-two input. The stage-two input consists of macros -- Stage-two Macros -- that generate control tables and conditionally assemble the necessary program modules; also, the stage-two input contains data constants, job control language (JCL) for stage two, and linkage editor control statements.

In order to provide the two-primary channel adapter feature, it has been necessary to modify some of both the Stage-one Macros and the Stage-two Macros. The remainder of this report is a brief description of the changes that have been made to each of the macros. Stage-one Macros. BUILD.

Prior to modification the "SECCHAN=" operand -- which specifies the use of the secondary channel adapter -- could have either the value "INACTIVE" (adapter not being used) or "BACKUP" (backup for primary channel). Now the user may also code "SECCHAN=ACTIVE" if he wishes both channel adapters to operate concurrently. NBUILD.

The NBUILD macro is an inner macro of the BUILD macro. If the user has coded "SECCHAN=ACTIVE" in the BUILD macro, a global SETB symbol, &SISFTRB(57), is set to 1 in the NBUILD macro. This global SETB symbol is then used by other macros to generate the modifications necessary for two primary adapters. This will be discussed in some detail in what follows. NGENEND.

NGENEND calls appropriate Stage-two Macros including SYSCG010 (see below); and SYSCG010 is one of the Stage-two Macros that has been modified. An additional operand, "SECTYP2=", has been included in the operand field of SYSCG010 to indicate whether the second channel adapter is active or backup. NGENEND, through a series of PUNCH statements, sets up the macro call for

1

Page 2 of 4

SYS...