EXECIO DISKW Question
Hello List, We want write a REXX EXEC , that do a Update in place. Another words, I need, read the record 1 from the file, and then rewrite the same record. Is possible? Thanks, Sergio
Re: EXECIO DISKW Question
Yes, but be careful. Try: EXECIO 1 DISKRU ... -Chip- On 6/1/11 14:49 Sergio Lima said: Hello List, We want write a REXX EXEC , that do a Update in place. Another words, I need, read the record 1 from the file, and then rewrite the same record. Is possible? Thanks, Sergio
Re: EXECIO DISKW Question
On Wednesday, 06/01/2011 at 10:50 EDT, Sergio Lima sergiovm...@hotmail.com wrote: We want write a REXX EXEC , that do a Update in place. Another words, I need, read the record 1 from the file, and then rewrite the same record. Is possible? Yes. There are a few programming considerations: 1. If the file is RECFM F, you can change any record you want. 2. If the file is RECFM V, you can change any record you want. 3. If you change the LRECL of a record in a RECFM V file, that record will become the last record in the file. 4. If other virtual machines have the disk accessed while you're doing this, then you can use filemode number 6 to cause the records to be physically rewritten to the same disk location. 5. Update-in-place using fm6 exposes the file to corruption if the system or CMS dies in the middle of a write. For more information, please read these (sub)sections of Ch. 9 (CMS File System) of the CMS Application Development Guide for Assembler - Replacing Records - EDF Data Integrity - Extending the file Alan Altmark z/VM and Linux on System z Consultant IBM System Lab Services and Training ibm.com/systems/services/labservices office: 607.429.3323 mobile; 607.321.7556 alan_altm...@us.ibm.com IBM Endicott
Re: EXECIO DISKW Question
Read up also about FILEMODE 6. And be sure that the file being updated has RECFM F (fixed record format), not RECFM V (variable). Once you are satisfied that you have it working, run some performance tests comparing: - updating that file vs - reading in the whole file, replacing just that record, and re-writing the whole file using CMS Pipelines. You may be surprised (depending on the file size, your disk subsystem, etc.). Mike Walter Aon Corporation The opinions expressed herein are mine alone, not my employer's. Chip Davis c...@aresti.com Sent by: The IBM z/VM Operating System IBMVM@LISTSERV.UARK.EDU 06/01/2011 10:28 AM Please respond to The IBM z/VM Operating System IBMVM@LISTSERV.UARK.EDU To IBMVM@LISTSERV.UARK.EDU cc Subject Re: EXECIO DISKW Question Yes, but be careful. Try: EXECIO 1 DISKRU ... -Chip- On 6/1/11 14:49 Sergio Lima said: Hello List, We want write a REXX EXEC , that do a Update in place. Another words, I need, read the record 1 from the file, and then rewrite the same record. Is possible? Thanks, Sergio The information contained in this e-mail and any accompanying documents may contain information that is confidential or otherwise protected from disclosure. If you are not the intended recipient of this message, or if this message has been addressed to you in error, please immediately alert the sender by reply e-mail and then delete this message, including any attachments. Any dissemination, distribution or other use of the contents of this message by anyone other than the intended recipient is strictly prohibited. All messages sent to and from this e-mail address may be monitored as permitted by applicable law and regulations to ensure compliance with our internal policies and to protect our business. E-mails are not secure and cannot be guaranteed to be error free as they can be intercepted, amended, lost or destroyed, or contain viruses. You are deemed to have accepted these risks if you communicate with us by e-mail.
Re: EXECIO DISKW Question
We want write a REXX EXEC , that do a Update in place. Another words, I need, read the record 1 from the file, and then rewrite the same record. Is possible? In addition to reading the manuals that Alan suggested, you should look for the RXFILEIO package on the VMWorkshop tapes. It provides CMS filesystem I/O interfaces that are much more natural REXX function interfaces to the CMS file I/O macros. You probably could also use the CMS common I/O routines, but they're a lot harder to understand and use.
