Technical data

SDA Description
2.3 Building the SDA Symbol Table
After locating and reading the system dump file, SDA attempts to read
the system symbol table file into the SDA symbol table. This file, named
SYS$SYSTEM:SYS.STB by default, contains most of the global symbols used
by the operating system. SDA also reads into its symbol table a subset of
SYS$SYSTEM:SYSDEF.STB, called SYS$SYSTEM:REQSYSDEF.STB, that it
requires to identify locations in memory.
If SDA cannot find the system symbol table file, or if it is given a file that is not
a system symbol table in the /SYMBOL qualifier to the ANALYZE command, it
halts with a fatal error.
When SDA finishes building its symbol table, it displays a message identifying
itself and the immediate cause of the crash. In the following example, the cause
of the crash was an illegal exception occurring at an IPL above IPL$_ASTDEL or
while using the interrupt stack.
Dump taken on 28-Jan-1993 18:10:09.79
INVEXCEPTN, Exception while above ASTDEL or on interrupt stack
2.4 Executing the SDA Initialization File (SDA$INIT)
After displaying the crash summary, SDA executes the commands in the SDA
initialization file, if you have established one. SDA refers to its initialization
file by using the logical name SDA$INIT. If SDA cannot find the file defined as
SDA$INIT, it searches for the file SYS$LOGIN:SDA.INIT.
The initialization file can contain SDA commands that read symbols into SDA’s
symbol table, define keys, establish a log of SDA commands and output, or
perform other tasks. For instance, you might want to use an SDA initialization
file to augment SDA’s symbol table with definitions helpful in locating system
code.
If you issue the following command, SDA includes those symbols that define
many of the system’s data structures, including those in the I/O database:
READ SYS$SYSTEM:SYSDEF.STB
You might also find it very helpful to define those symbols that identify the
modules in the images that make up the executive. You can do this by issuing the
following command:
READ/EXECUTIVE SYS$LOADABLE_IMAGES
After SDA executes the commands in the initialization file, it displays its prompt,
as follows:
SDA>
The SDA> prompt indicates that you can use SDA interactively and enter SDA
commands.
An SDA initialization file can invoke a command procedure with the @ command.
However, such command procedures cannot themselves invoke a command
procedure (that is, you cannot have nested command procedures).
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