2.7 Special considerations
This section contains more information on the trickiest parts of CJLI as well as some useful hints for application programmers.
LISTSERV treats anything mailed to the LISTSERV userid as a set of commands to execute. Thus, as soon as an unknown command is encountered in the job stream, the whole physical job file (not just the current job) is immediately flushed and discarded. This avoids 'executing' hundreds of unknown commands and sending back a huge job output when a regular mail file is sent to the LISTSERV userid by someone who thought it would be distributed to a list. Note that errors from known commands do not cause termination of the job -- only completely unknown commands such as "Hiya!!" would terminate the job.
Although CJLI is based on the network standard 80-characters card images, LISTSERV accepts command jobs in several network formats, including Disk Dump and Netdata. In that case it will accept records of up to 255 characters as input, and you may find this very convenient when sending long commands to the server.
Alternatively, continuation cards can be used to split long commands into several 80-characters cards. In that case you must insert a "// " string before the command text so that CJLI considers it as a control card and performs the required concatenation; it will then realize that the "card name" is unknown and transform the card into a regular command card. If you opt for that method, you will find the "//+" continuation card feature very convenient for a program (but not for a human person). This method is used by LISTSERV when transmitting "DISTRIBUTE" commands to other LISTSERVs.
There is no limit at all on the final size of a control card, i.e., on the number of continuation cards you can specify; however, you must make sure that no line in any of the 'datasets' ever exceeds 255 characters. In particular, if the physical job file is sent in Netdata format, you must make sure that the file lrecl is not higher than 255.
Note: For LISTSERV on z/VM: Due to internal coding considerations, it is recommended that physical job files be sent to LISTSERV in PUNCH format. This will make it easier for the ‘outer’ interface to detect the job file for what it is and will save some CPU time to the server, thereby improving job response time. Please keep in mind that DD lines longer than 80 characters cannot be sent in PUNCH format.
For more information on how to send commands to LISTSERV for execution, see the standard LISTSERV documentation.