GDSX Manual

Design and Development
Extended General Device Support (GDSX) Manual–134303
2-16
Data Declarations
Data Declarations
TSCODE sources in global data declarations from the DCCBDECS, DGCBDECS, and
PEXTGDS files of the installed subvolume. These declarations define:
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Configuration parameters
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Control block tables
•
Memory pools
•
Resource maps
•
SPI definitions
Some of these declarations are public to USCODE (user code can source them in at
compile time). The data structures accessible to user code are:
•
I/O control block template (iocb^template)
•
Device control block template (dcb^template)
•
Task control block template (tcb^template)
•
Line control block template (lcb^template)
•
Receive control block template (rcb^template)
•
File control block template (fcb^template)
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Device control block address table (DCBTBL global)
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Task control block table (TCBTBL global)
•
Line control block table (LINETBL global)
•
File control block table (FCBTBL global)
•
Map template structure for resource map usage
•
Configuration data template
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Event mask definitions and event result literals
•
Guardian file error code literals
User Code Declarations
Because multiple copies of a USCODE procedure can be running at the same time in a
multithreaded GDSX environment, USCODE variables must be defined properly. If the
value of a variable is unique for each task at run time, declare the variable as a local
variable. If a variable must be shared among tasks, declare the variable as a global. For
read-only globals, the shared extended pool (see "Memory Pools" on page 2-23) may be
Caution. Before altering a global used by TSCODE, make sure you know what TSCODE is
doing with it.