Re: Rexx address command versus execsql

[Simon Coulter <shc@xxxxxxxxxxxxxxxxx>]

On 03/04/2008, at 8:47 AM, Tom Liotta wrote:

> One thing that isn't clear to me is what happens when repeated
> ADDRESS statements refer to the _same_ environment that is already
> saved as the 'permanent' environment. I.e., what is the result of
> saying ADDRESS COMMAND when COMMAND is already the environment?

Has no effect. Rexx supports 3 environment states: ACTIVE, ALTERNATE,  
and TRANSIENT.

ACTIVE is either the one it starts with or the one assigned via  
ADDRESS env-name. ALTERNATE is the one that existed prior to a  
change. At program start ACTIVE and ALTERNATE are the same. TRANSIENT  
is the environment used for the running of a specific command or  
statement such as:

	ADDRESS *COMMAND 'DSPMSG'

This environment lasts only for the duration of the statement.

If ACTIVE is currently *COMMAND and you issue ADDRESS COMMAND then it  
stays ACTIVE. Effectively a NO-OP.

> And then what happens when a later ADDRESS EXECSQL is thrown in?

*EXECSQL becomes the ACTIVE environment and the previous becomes the  
ALTERNATE. Issuing ADDRESS on its own toggles between them.

> And what happens when the environment is reverted back to the  
> previous?

In what way. The previous is now the ACTIVE and the old active is now  
the ALTERNATE.

It gets a bit messier with *COMMAND, *EXECSQL, and *CPICOMM in the  
same Rexx program because only one can be ACTIVE, one can be  
ALTERNATE and the other is simply dropped. In these cases you would  
set ACTIVE and ALTERNATE to the most used and use TRANSIENT for the  
other(s).

Regards,
Simon Coulter.
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