6. DATA SOURCES › 6.6 I/O Measurements and Device Activity › 6.6.3 I/O Measurements › 6.6.3.3 APPC/MVS Data Transfer Elements

6.6.3.3 APPC/MVS Data Transfer Elements

APPC/MVS enables program-to-program communication on a "peer-
to-peer" basis.  This cooperative processing support allows
conversations between transaction programs (TPs) running
anywhere in the SNA network.  Once a conversation is
established, the TPs can send and receive data using APPC
services.  Any TP executing in the MVS environment records
the data sent and received, to and from the partner TP.  If
the TP is a batch job, TSO session, started task, or APPC/MVS
ASCH scheduled TP, the data sent and received is recorded in
the BATPGM, BAT_TS, BAT_ST, or BAT_TP file in the following
data elements:

PGMDATAR - APPC Data Received (Bytes)
PGMDATAS - APPC Data Sent (Bytes)

If the TP is a batch job step, then a job-level observation
will also be found in the BATJOB or BAT_JS file.  The job-
level data elements that record APPC data sent or received
are:

JOBDATAR - APPC Data Received (Bytes)
JOBDATAS - APPC Data Sent (Bytes)

Finally, if the MVS TP is an APPC/MVS ASCH scheduled TP, the
APPC/MVS Transaction File (BATATP) records contain the amount
of data sent and received by the TP.  Records appear in both
the BAT_TP and BATATP file for the same execution of an
APPC/MVS ASCH scheduled TP.  Each BAT_TP record represents
the address space perspective of a TP execution, while each
BATATP record represents one invokation of a given TP.  In
the case of multi-trans scheduled TPs, the TP remains in
execution between conversations with requesting partner TPs.
This means that a single BAT_TP DETAIL timespan observation
can contain the cumulative resource measurements from many
different conversations with various partner TPs.  In the
BATATP file, on the other hand, each observation contains the
resource utilization of a single conversation with the
requesting partner TP.

The APPC data sent and received by an ASCH scheduled TP is
captured in the following BATATP file data elements:

ATPDATAR - Data Received (Bytes)
ATPDATAS - Data Sent (Bytes)

Duplicate accounting issues exist with the APPC Data Sent and
APPC Data Received data elements.  The data sent by one TP is
data received by the partner TP.  When both TPs execute in an
MVS environment, SMF records document the sent and received
metrics twice: once from the sending perspective, and once
from the receiving perspective.  This duplicity occurs in two
BATATP observations when the APPC managed conversation was
between two ASCH initiated TPs.  It occurs in one BATATP and
one BATPGM, BAT_ST, or BAT_TS observation (with the PGMDATAR
and PGMDATAS data elements) when the APPC managed
conversation was with an ASCH initiated TP allocated by a
batch job, started task, or TSO session.

Charging only for data received or data sent would avoid the
duplicity problem for conversations between two TPs executing
in an MVS environment.  When the conversation is between one
MVS TP and another TP executing executing in a non-MVS
environment (e.g., a PS/2 workstation or an AS/400), however,
it would be valid to charge for both data sent and received
on the MVS side if the partner TP environment did not support
chargeback.

The issue is further complicated because a single TP can
allocate multiple conversations with several different
partner TPs.  The multiple conversations can be spread across
a number of different execution platforms: some that record
data traffic and others that do not.

Careful consideration should be given to these duplicate
chargeback issues before deciding to use the Data Received
and Data Sent data elements as costing elements in the Batch
Information Area files.