> -----Original Message----- > From: IBM Mainframe Discussion List > [mailto:IBM-MAIN@bama.ua.edu] On Behalf Of Farley, Peter x23353 > Sent: Friday, April 20, 2012 8:02 AM > To: IBM-MAIN@bama.ua.edu > Subject: Re: USS File Integrity > > 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.
I will disagree with you on this point. I would use the z/OS ENQ facility. It is fully supported by the ZFILE portion of the JZOS software, which is a part of the IBM supplied Java language on z/OS. And we all, hopefully, know that using ENQ allows for sysplex-wide serialization. http://www.ibm.com/developerworks/java/zos/javadoc/jzos/index.html > > 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? Yes, it can: http://docs.oracle.com/javase/6/docs/api/java/nio/channels/FileLock.html Of possible interest is the statement: This file-locking API is intended to map directly to the native locking facility of the underlying operating system. Thus the locks held on a file should be visible to all programs that have access to the file, regardless of the language in which those programs are written. > > Peter -- John McKown Systems Engineer IV IT Administrative Services Group HealthMarkets(r) 9151 Boulevard 26 * N. Richland Hills * TX 76010 (817) 255-3225 phone * john.mck...@healthmarkets.com * www.HealthMarkets.com Confidentiality Notice: This e-mail message may contain confidential or proprietary information. If you are not the intended recipient, please contact the sender by reply e-mail and destroy all copies of the original message. HealthMarkets(r) is the brand name for products underwritten and issued by the insurance subsidiaries of HealthMarkets, Inc. -The Chesapeake Life Insurance Company(r), Mid-West National Life Insurance Company of TennesseeSM and The MEGA Life and Health Insurance Company.SM ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
