Guardian Procedure Errors and Messages Manual

errors relating to operations involving open files; the last error associated with the file number is
returned.
A typical method of testing for an error and calling FILEINFO to get the error value might appear
as follows:
IF <> THEN ! If CCL or CCG occurred, then
CALL FILEINFO ! call this procedure to get the error value.
Interprocess Messages
Interprocess messages are data structures that are exchanged between processes or between the
operating system and a process. Interprocess message are received by a user process through its
$RECEIVE file. A user process sends an interprocess message by opening the process to which the
message is to be sent.
This manual describes the following two types of interprocess messages:
• Interprocess command interpreter messages
• System messages
Interprocess Command Interpreter Messages
An interprocess command interpreter message is an interprocess message that is exchanged
between the command interpreter and an application process. The Tandem Advanced Command
Language (TACL) command interpreter is supplied by HP for use on the operating system.
Use of interprocess command interpreter messages is documented in the Guardian Programmer's
Guide.
System Messages
A system message is an interprocess message that is sent from the operating system to an application
process. Use of these messages is documented in the Guardian Programmer's Guide.
Error Lists
Error lists are Subsystem Programmatic Interface (SPI) buffers returned to an application program
by another process. Error lists can be returned to your application process if you are using SPI to
send requests to another process. If the other process encounters a procedure error, it returns the
error information in an error list to your application process.
Error List Content
Unlike the error messages described elsewhere in this manual, error list information is returned in
the form of tokens that are meaningful to application processes rather than in the form of displayable
text. The content of error lists can vary; for example:
• A response record can contain both response data and error or warning information.
• A single response record can contain multiple error lists, especially if warnings occur.
• A single error can actually be a pass-through error, an error that originated in another
subsystem that was called by the subsystem to which the command was sent.
Figure 1 shows the format of an error list.
Figure 1 Error List Format
Interprocess Messages 17