Thanks Wally – thats great.
From: [email protected] [mailto:[email protected]] On Behalf Of Wally Terhune Sent: 31 May 2009 02:03 To: U2 Users List Subject: Re: [U2] unidata hangs >From the 7.1.15 readme: Issue 9809 - Problem Description UniData -- UniData maintains a table in shared memory that records information about your system's file systems and the available space in each file system. This table is used to quickly determine if a dynamic file has room to expand in its current directory or if a new part file needs to be created in another file system. The table is loaded when the database starts and is refreshed regularly by the smm daemon. Prior to this release, the smm daemon created entries in this table by forking the UNIX 'df' command. As smm relied on the specific format produced by the standard OS-provided df command, if an administrator replaced the standard 'df' command with a different df utility, smm was unable to properly parse the df output and create proper entries in the shared memory table. This could result in the inability to create or expand UniData dynamic files. This table can be viewed with the '$UDTBIN/sms -F' command. Here is an example of the normal, expected output: # $UDTBIN/sms -F File system table size (N_FILESYS):200, Used: 13 Device ID Available Space NFS File System Name (in 512 Bytes) 1073741827 621296 no / 1073741825 755264 no /stand 1073741833 1209600 no /var 1073741834 1736512 no /usr 1073807361 91514582 no /tshp1123 1073741832 1002224 no /tmp 1073741831 1027440 no /opt 1073741830 1320720 no /home 1073741829 9326052 no /disk2 1073741828 2599142 no /disk1 Starting with this release, smm no longer forks df to create the entries in this table. Instead, smm reads the platform-appropriate mount table to create the file system entries in this table. As smm does not fork a df command, any problem with the output format of a non-standard df command is avoided. In order to provide compatibility with prior releases, a new parameter is created in udtconfig: USE_DF. The default setting for this parameter is: USE_DF=0. This means 'use the new method of loading the shared memory table by reading the mount table'. If an administrator prefers to have smm continue to fork df (as in prior releases), they can set udtconfig USE_DF=1. UniData daemons must be stopped and restarted to implement any change to the USE_DF setting. NOTE: There have been a number of other problems associated with smm forking df, including: smm core dumping; defunct df processes spawned by smm. Most of these problems were triggered by the behavior of 'df' when nfs-mounted files systems became unavailable to the system. As smm no longer forks df, these problems should no longer occur at this release. ADDITIONAL NOTE: Customers have sometimes experienced a problem with a udt process hanging during initialization when an nfs mounted partition was unavailable (network or system down). This behavior may not be completely resolved by the fix for this issue. This hang was due to smm not responding to the login request from the udt process - typically because it was hung itself, waiting for a df process to complete. Even though we now avoid forking df, smm still re-calculates the space available in each file system every 60 seconds (by default). smm uses a standard UNIX statfs() system call to determine the space available on a file system. If smm is checking an nfs file system that is unavailable, that system call may still hang. The behavior of this varies by UNIX flavor. If you mount nfs file systems as a HARD mount, this system call may hang until that remote system becomes available again. smm will wait on that system call as well. IBM recommends that you consider using SOFT nfs mounts. There is typically a configurable number of retries that will be attempted before the system call returns with a failure status. This allows smm to continue after a brief pause, waiting for statfs() to return. Please consult your UNIX support provider for specific information about NFS SOFT mounts for your platform. Wally Terhune U2 Support Architect IBM Information Management Software Tel: (303) 773-7969 T/L 656-7969 Mobile: (303) 807-6222 Email: [email protected] http://www.ibm.com/software/data/u2/support Inactive hide details for "Symeon Breen" ---05/30/2009 05:34:50 PM---Why why why do all unidata processes hang when a mount poi"Symeon Breen" ---05/30/2009 05:34:50 PM---Why why why do all unidata processes hang when a mount point dies - even if the mountpoint is not be From: "Symeon Breen" <[email protected]> To: <[email protected]> Date: 05/30/2009 05:34 PM Subject: [U2] unidata hangs Sent by: [email protected] _____ Why why why do all unidata processes hang when a mount point dies – even if the mountpoint is not being used by any udt process ??? This drives me potty – it has happened again today where a mount for some data sharing went down because the other machine had a network problem. This mount was not used by any udt process just used at linux to copy some files etc. Every udt process, telnet sessions, phantoms, uniobjects processes then hangs. I have had to unmount the offending mount and stop and start unidata killing off all sorts of things ! Is there a way to stop this happening ? a different type of mount, a udt param, a udt upgrade (we are on 7.1) Cheers Symeon. _______________________________________________ U2-Users mailing list [email protected] http://listserver.u2ug.org/mailman/listinfo/u2-users
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