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3380 Record Format in Airline Environment

IP.com Disclosure Number: IPCOM000105631D
Original Publication Date: 1993-Aug-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 4 page(s) / 110K

Publishing Venue

IBM

Related People

Legvold, VJ: AUTHOR

Abstract

The Transaction Processing Facility (TPF) is the operating system used in the Airline Environment. The TPF data base organization depends on the track capacity. The predominate device type currently being used is 3380. To migrate to a new device type with a different track capacity requires re-organizing the entire data base.

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3380 Record Format in Airline Environment

      The Transaction Processing Facility (TPF) is the operating
system used in the Airline Environment.  The TPF data base
organization depends on the track capacity.  The predominate device
type currently being used is 3380.  To migrate to a new device type
with a different track capacity requires re-organizing the entire
data base.

      To minimize the conversion effort when installing the 3990
Control Unit, with the Airline RPQ attached to 3390 devices, 3380
Track Compatibility Mode is used.  This allows the user to
re-organize the data after the hardware conversion is complete.

      Since TPF will access only a single record or a single track
with each Start I/O there is no negative performance impact when
using 3390 devices in 3380 Track Compatibility Mode instead of in
Native Mode.  This fact will cause many users to delay the data base
re-organization required to use the native mode until additional
storage is required.  Using native mode will increase the capacity of
the data base.

      The base 3990 control unit does not support 3380 Track
Compatibility Mode devices when accessed from Escon channels.  The
Device Support Facility (DSF) software package, which is required for
device maintenance, also does not support 3390s running in 3380 Track
Compatibility Mode when accessed by Escon channels.  Background

      With 3380 Track Compatibility Mode the records are spaced
evenly around the track.

      Additional processing is required during the gaps (space
between fields) with a 3390 operating in 3380 Track Compatibility
Mode.  With the overhead of Escon, enough time does not exist in the
gap to perform the required processing when running with the cache.

      For records without keys and data lengths of at least 289
bytes, a 3390 track will hold at least as many records as a 3380
track.  With smaller data lengths the 3380 can hold more records on a
track than a 3390.  With 3380 Track Compatibility Mode the gap sizes
of small records are reduced and this allows the 3390 to write the
same number of records on a track as a 3380.

      The data accessed by TPF will also be accessed by MVS and VM
systems to perform diagnostic and testing functions.

      TPF supports three record sizes.  All devices are formatted
identically and the data base is spread out across all devices.  A
record is assigned a relative record number and knowing this number
plus the number of devices in the complex and the device
characteristics, a physical location (device/cylinder/head/record
number) can be calculated.

      The three record sizes supported by TPF are 381, 1055 and 4096.
Figure 1 shows the number of each sized records that will fit on 3380
and 3390 devices.

      The Figure shows that in all cases for TPF more records will
fit on a 3390...