> In the normal course of events, how quickly would "dirty" > pages be posted from memory to disc? Would flat files and TI > datasets be treated the same way? > In the event of a system failure, how are "dirty" pages handled, > if at all? > We need to understand just how protected we are in a process > that movesrecords from a primary data base to an archive data > base. Leonard, In "the normal course of events" Transaction Manager XM performs two postings to disc; your TurboIMAGE (TI) data will be fully protected after the first posting is completed. XM maintains data structure in memory, known as the XM Journal, which is really the memory resident portion of the XM log files stored on every volume set master. TI transactions that transform the database (e.g., DBPUT, DBDELETE, etc.) are recorded in the journal before they are committed to disc. The XM journal file is posted to XM disc log files when one of the following occurs: o The XM Journal is full; the journal can store up to 64KB. o Time expiration -- anything from 0.12 to 1 second. o Block-on-commit, i.e., a process is waiting for the post to occur. o Too many frozen pages. Pages containing the actual TI data are frozen in memory until the XM Journal is posted. This means these dirty frozen pages cannot be posted to disc until the journal is posted. YMMV as to when XM Journal post is performed and your TI data is protected. I believe the maximum wait would be 1 second. As long as this XM Journal post takes place, XM will be able to post the dirty pages to disc even after a soft system failure (i.e., a failure in which you don't loose a disc). Dirty pages get posted back to disc during a XM checkpoint that occurs when: (i) the system or user XM log files on disc are half full, or (ii) the volume set is closed, or (iii) system is shutdown with a CNTRL-A. Since MPE/iX 6.5 the size of these both these XM log files became user configurable, so once again YMMV as to when a checkpoint will occur. Remember, that this posting of dirty pages, while comforting, is NOT required for complete TI transaction protection. Now, what about flat files? In the normal course of events they are NOT protected by XM. You can protect these files by attaching them to the serial write queue using the FSETMODE (bit 15) intrinsic. Hope this helps, and thank you for showing me that the stuff I used to teach in the MPE/iX Performance and Tuning course is still useful :-) Take care, frank ====================================================== Frank Alden Smith HP MPE/iX Certified Professional Alden Research, Inc. Instructor -- Consultant 3617 Ligon Road Ellicott City MD 21042 Phone: (410) 750-2101 "All knowing is doing" -- Humberto Maturana (biologist and teacher) ====================================================== * To join/leave the list, search archives, change list settings, * * etc., please visit http://raven.utc.edu/archives/hp3000-l.html *