vtam การใช้

• In modern terminology, VTAM provides a communication stack and device drivers.
• However, VTAM 2 was the last version to be freely available.
• VTAM and SNA are still in use by many enterprises.
• IBM introduced VTAM ( Virtual Telecommunications Access Method ) with the System / 370.
• Originally, VTAM was provided free of charge like most systems software of that time.
• Initially, VTAM only allowed communication between mainframes and peripheral equipment such as terminals, distributed processors and minicomputers.
• VTAM provides an application programming interface ( API ) for communication applications, and controls communication equipment such as adapters and controllers.
• VTAM supports several network protocols, including Bisync, local ( channel attached ) 3270 devices, and later TCP / IP.
• In IBM terminology, VTAM is an access method software allowing application programs to read and write data to and from external devices.
• VTAM is also supported by IBM, as is the IBM Network Control Program ( NCP ) required by the 3745 / 3746 controllers.
• As such, VTAM is comparable with VSAM, which was at that time a new and supposedly converged access method for disk storage.
• ACF / VTAM ( Advanced Communication Function / Virtual Telecommunications Access Method ) was introduced in 1976 and was provided for a licence fee.
• This also applies to TCP / IP, DB2, VTAM, to a certain extent language support and even basic disk I / O.
• In addition to the previous DCB support, with this reinstatement of TCAM support, CICS began to support TCAM access via VTAM, also known as the ACB support.
• The major new feature of ACF / VTAM was the " Multisystem Networking Facility ", which introduced " implementation of intersystem communication among multiple S / 370s . ".
• This protocol allows existing VTAM applications ( CICS, TSO ) to run with little or no change from traditional SNA by supportng traditional 3270 terminal protocol over the TCP / IP session.
• "' Virtual Telecommunications Access Method "'( "'VTAM "') is the IBM subsystem that implements Systems Network Architecture ( SNA ) for mainframe environments.
• The bi-sync handler was only 4k, in contrast to IBM's BTAM at 28k, QTAM at 36k, and TCAM at 42k, and VTAM which started at 48k.
• VTAM was supposed to be the successor to the older telecommunications access methods, such as Basic telecommunications access method ( BTAM ) and Telecommunications Access Method ( TCAM ), which were maintained for compatibility reasons.
• GCS's purpose is to provide an environment to run some specific CMS, the usual VM guest, already has OS simulation, it is not extensive enough to run some applications such as VTAM.