any files open after you have altered it. Files opened prior to your changing the setting will have been opened using (cont.)<br />the old setting.<br />The *READ command can be issued at any time to change the default open type to OPENR (open for read-only). If your (cont.)<br />program is a report program which never needs to update any records on any files, you should issue the *READ command (cont.)<br />near the top of your processing logic so that all files will be opened read-only.<br />The *LOAD command can be used to reset the default open type to OPENU. Your program can issue the *LOAD and *READ commands any number of times throughout its processing.<br />Please not that these commands affect only implicit opens. Also note that explicit opens neither affect the default setting not are affected by it.<br />## <br />Explicit Opens<br />Several commands are provided for your programs to explicitly open a file. In the CICS environment all of these are ignored and treated as a NOOPS (no operation).<br />The OPENR command will open a file for read-only.<br />The OPENU command will open a file for input-output, allowing updates.<br />The OPENO command will open a file for output, intiializing the file.<br />The OPENE command will open a file "extended". This is valid only for a sequential file and allows you to add records to the "end" of the file.<br />The OPENX command will open a file for exclusive input-output. That means that no other user on the network will be (cont.)<br />able to access that file until you have closed it or reached end-of-job. This command has meaning only on a LAN/WAN and (cont.)<br />is equivalent to OPENU if issued on a mainframe. Opening exclusively will greatly speed your processing sicne not (cont.)<br />sharing logic will be executed.<br />## <br />Explicit Closes<br />When an online program completes a transaction, sneding the screen to the operator, an implicit close is done (except (cont.)<br />in CICS) on all files that were left open. They will automatically be reopened with any positioning restored for the (cont.)<br />next transaction if needed. Explicit closes can be done prior to the end of your transaction, if you wish, to minimize (cont.)<br />resource consumption.<br />Batch programs also have their files closed implicitly at end-of-job. You can issue explicit closes to enable reopening (cont.)<br />the file differently. For example, if you have created a new file by opening for output, you may want to close it and (cont.)<br />reopen it using OPENU to be able to access and update records on that file.<br />The *CLSE command will close all files that are open and will issue a COMMIT to ensure that all data is flushed from file buffers and saved to disk.<br />The CLSFL, or CLOSE (they are synonyms) commands will close an individual file.<br /># <br />Appendix H -- Sequential Files<br />To define a sequential file to MAGEC, use the access method SEQDS, SEQCMPR, OR SEQCRLF on the DCL definition. SEQDS (cont.)<br />specifies a fixed-length, non-compressed file. SEQCMPR specifies a compressed sequential file using the intrinsic (cont.)<br />compression facilities of the environments file systems (usually, MicroFocus Cobol). SEQCRLF specifies a sequential (cont.)<br />text file using Carriage Return-Line Feed ASCII characters to denote end-of-record.<br />Sequential files can be accessed using MAGECIO, however only certain commands can be issued against them. Obviously, (cont.)<br />without an index many of the facilities available to VSAM or other indexed access methods cannot be (cont.)<br />provided.<br />All of the explicit open commands are supported for sequential files, including OPENE, but excluding OPENI.<br />All of the close commands are supported.<br />The only read command supported is REDNX, which, for a sequential file requires no prerequisite except for an open.<br />The ADDIT command is used to write to a sequential file.The file must have been opened using OPENE.<br />The UPDAT command is used to rewrite a record to a sequential file.<br />If you issue a database command that is not supported for sequential files, though it is a valid command for other file types, you will be issued a return code of '1S' in TWA-DB-RETURN-CODE.<br />## <br />Generic File Names<br />MAGEC in the PC environment allows you to define and access files using generic names. A generic name is one which (cont.)<br />includes one or more (maximum 7) question marks as the trailing characters of the file name. For example: (cont.)<br />FILE???.TXT.<br />At the time that your program first accesses the file using either an explicit or implicit open (REDNX, OPENR, or (cont.)<br />OPENX) MAGEC's IO module will access the directory of the PC file system (may be either a LAN or local file) to (cont.)<br />determine whether there are any files whose names match the generic name given, and which file name to use. In the case (cont.)<br />of an input file that means that there may be several files with matching names, i.e.: FILE001.TXT, FILE002.TXT, (cont.)<br />FILE003.TXT, etc.<br />The IO module will access the directory and will open the first (lowest in collating sequence) file. In this example (cont.)<br />FILE001.TXT. When you program reads to the physical end of FILE001.TXT, the IO module will again access the directory (cont.)<br />to obtain the next lowest file name and will open it as if it were concatenated to the first file, and so (cont.)<br />forth.<br />In order to avoid conflicts, the IO module renames the input file using an extension of "_IN" before opening it, and (cont.)<br />renames it using another extension immediately after it is closed. The extension used for this final rename operation (cont.)<br />is taken from the KYF description in the "Extension after file is processed" specification. The extension given here (cont.)<br />should not be the same as the original extension and should not be "_IN". For example, a good choice for Extension (cont.)<br />after file is processed would be "DUN" (for "done").<br />As you can see, using this scheme would mean that the IO module would first find FILE001.TXT, rename it to FILE001._IN, (cont.)<br />and open it for your program. When you have read through that file, it would rename it as FILE001.DUN and re-access the (cont.)<br />directory to find the new lowest file name matching the FILE???.TXT generic name. That would probably be ("probably" (cont.)<br />because of the possibility for multiple workstations to be performing the same process as discussed below) FILE002.TXT. (cont.)<br />Your program will read through several concatenated files as if they were one.<br />## <br />Multiple Concurrent Processing<br />Using this scheme it is possible for several (unlimited number) of workstations attached to a server to concurrently (cont.)<br />process a "pool" of transaction files. The same program could be executing on each workstation processing the (cont.)<br />transactions against the same database or master files. Since the files are renamed before and after processing, other (cont.)<br />workstations will not recognize them as input files. Therefore, one workstation might process FILE001.TXT, then another (cont.)<br />might begin processing FILE002.TXT. When the first reaches the physical end of FILE001 it will automatically begin (cont.)<br />processing FILE003.TXT.<br />## <br />Generic Output Files<br />In the case of generic file names for output files, the IO module will access the directory to determine the highest (cont.)<br />file name which currently exists matching the generic name. It will add one to the numeric (generic) portion of the (cont.)<br />file name and will open it for output using a temporary extension of "_OT". When your program closes the file the IO (cont.)<br />module renames it using the extension specified in the File specification,<br />not the "Extension after file is processed"!<br />Multiple workstations could be creating files using the generic name and each will automatically use a unique name. (cont.)<br />They would likely be creating a pool of transaction files which will later be accessed as described (cont.)<br />above.<br />If you wish to write files using generic names your program must issue an explicit OPENO and an explicit CLOSE command.<br />## <br />Generic Name Formats<br />Only sequential files may be specified using generic file names. Indexed files may not. Sequential files are defined using the access methods: SEQDS, SEQCMPR, or SEQCRLF on the DCL definition.<br />A generic name is any name including question mark characters (?) as the last characters of the name (not the (cont.)<br />extension). The question marks must be contiguous and may not be followed by any other character, except for the dot (cont.)<br />(.) which separates the name from the extension. There may be from one to seven question marks. The actual file names (cont.)<br />represented by the generic name must have numeric characters (1 - 9) in the positions held by the question marks. For (cont.)<br />example:<br />A???????.TXT (files: A0000001 thru A9999999)<br />TRANS??.INP (files: TRANS01 thru TRANS99).