Availability Guide for Application Design

Designing Applications for Change
Availability Guide for Application Design—525637-004
10-26
Upgrading a TCP Requester
Refer to Section 4, Data Protection and Recovery, for additional details.
Upgrading a TCP Requester
Programs that execute under the TCP can be automatically upgraded to a new version
if the flags on the COBOL directory are set up to do so.
When the COBOL compiler generates a new version of a program, it adds the new
version to the program file and adds a corresponding entry in the COBOL directory.
Whether the new version of the program is invoked next time the program is called
depends on whether the old version is already in memory and on the setting of flags.
Using PATHCOM to Perform the Upgrade
If the old version of the program is not in memory when the program is invoked, then
the most recent version of the program is automatically used. If the old version of the
program is in memory, however, upgrade depends on flag settings.
The SET TCP CHECK-DIRECTORY command is used while configuring the TCP to
determine whether the application will perform a search of the COBOL directory every
time a program is called, to ensure that the most recent version is used. Setting this
option to ON ensures the most current version. Many HP users, however, prefer to set
this option to OFF because searching the directory can cause an unacceptable
performance reduction.
The REFRESH-CODE TCP command performs a similar function, but only once for
each program. It works only when the SET TCP CHECK-DIRECTORY parameter is set
to OFF. You issue this command when the TCP is running to cause a search of the
COBOL directory once for each program, the next time each program is called.
What Are the Design Implications?
To understand the design implications, consider the following example and its
associated call graph:
1. PROGA and PROGB perform some initialization before PROGB calls PROGC.
2. PROGC executes an infinite loop, periodically calling PROGD, PROGE, and
PROGF but never returns to PROGB.