I know CA-MIM , if memory serves me correctly works across Plexes and Lpars. I am not sure if it works across Unix file systems in a similar manner
Scott Ford Senior Systems Engineer www.identityforge.com On Apr 20, 2012, at 9:43 AM, David Crayford <dcrayf...@gmail.com> wrote: > Synchronizing file access between threads in a single program in java is > trivial. Java has a built-in synchronized methods to implement critical > sections. I'm not sure how well it would scale though as I guess there > implemented by calling the pthread API. > > On 20/04/2012, at 9:01 PM, "Farley, Peter x23353" > <peter.far...@broadridge.com> wrote: > >> The OP originally stated that he had two STC processes that updated the same >> z/Unix file at the same time and wanted to prevent this. Are two STC's both >> considered z/Unix processes under the same kernel when they are running on >> the same LPAR? If so, ISTM that locking and unlocking the file around the >> write code will work as a mechanism to prevent simultaneous writes. >> >> But what about two STC's running on different LPAR's in the same sysplex? >> Does z/Unix file locking work across LPAR's, or only within the same LPAR? >> >> Just curious. >> >> ISTR that simultaneous writes to a common file are classically solved in >> most unix systems by implementing a daemon process that is the only process >> allowed to write to the file, and other processes send messages to the >> daemon to accomplish the write function, like the syslog daemon for system >> messages. >> >> The new question is whether Java on z/Unix provides access to any file >> locking mechanism at all, as the OP also just said it was a Java application >> and he wants to share the file among tasks of the *same* program. That >> would argue that using whatever the Java equivalent of the C flockfile >> function is would be the solution to use. >> >> But can z/Unix Java do that? Or does he have to write a JNI function to be >> called from his z/Unix Java code to implement a file lock? Or should he >> just implement a third process/task under the same program for the file >> writes and have both of the other tasks just send messages to the write >> process? >> >> Peter >> >> -----Original Message----- >> From: IBM Mainframe Discussion List [mailto:IBM-MAIN@bama.ua.edu] On Behalf >> Of Walt Farrell >> Sent: Friday, April 20, 2012 8:27 AM >> To: IBM-MAIN@bama.ua.edu >> Subject: Re: USS File Integrity >> >> On Fri, 20 Apr 2012 11:18:45 +0800, David Crayford <dcrayf...@gmail.com> >> wrote: >> >>> Of course, fcntl() can be used to implement byte-range-locking. So in >>> theory you could use it to implement >>> row-level locking in a dictionary library. ENQ is not that granular. >> >> ENQ is as granular as the application wants to make it, depending on how >> clever the application programmer is at encoding information into the RNAME >> the application will use. >> >> The key point about UNIX files, though, is that all the locking is advisory, >> and controlled by the applications that use the file. If they all implement >> the same locking mechanism (whatever that may be), the locking will work. If >> they don't, it won't work. >> -- >> >> >> This message and any attachments are intended only for the use of the >> addressee and may contain information that is privileged and confidential. >> If the reader of the message is not the intended recipient or an authorized >> representative of the intended recipient, you are hereby notified that any >> dissemination of this communication is strictly prohibited. If you have >> received this communication in error, please notify us immediately by e-mail >> and delete the message and any attachments from your system. >> >> ---------------------------------------------------------------------- >> For IBM-MAIN subscribe / signoff / archive access instructions, >> send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
