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Status Future consideration
Categories z/TPF
Created by Guest
Created on Nov 19, 2019

Sync TPF File System tables in loosely coupled systems

We cleaned up the tpf file system in one of our sabre systems and noticed other processors didn't reflect the update with a ZFILE df -aic entry. I submitted a case (TS003005946) with the following response:

The numbers for these values sync up over time but can get out of sync. This is by design for performance reasons.
In the TFS, we use #IZERO record ordinals to track the free inodes. This is where we obtain the "inodes available"
information for our memory structures that are out of sync. In order to bring the numbers back into sync we need
to use (find) each of the #IZERO record ordinals. For a system with 1,000,001 #INODE ordinals you would have
1,000 #IZERO ordinals in use. As you create and delete files and directories in the TFS, the #IZERO records are
accessed regularly (once for each file creation or deletion). The #INODE ordinals are returned to the #IZERO where they
originated and are dispensed in a round robin fashion (typically). As we access the #IZEROs as part of allocating or
releasing an #INODE, we also update our processor specific memory tables with the latest available count
from the #IZERO. So a large number of allocates or releases on one processor will cause a skew in this number on the other
processor until that other processor has read in each of the #IZERO ordinals itself (or until you IPL).
If you wanted us to sync the tables that would be an enhancement .
We could either read all of the #IZERO record ordinals when the the zfile DF command is issued OR implement some sort
of sipcc sync up to other processors when a large number of changes are detected within a short amount of time.
Please open an RFE if you want this.

Idea priority Medium
  • Guest
    Reply
    |
    Apr 16, 2024
    From the IBM TPF Lab:
    You can use the ZFILE df command to display the number of in-use and available inode counts. The ZFILE df command uses a cached value in processor-unique memory for displays of the inode counts. The cached inode counts are updated when TFS processing code on each processor accesses each #IZERO record. Because the cached inode counts are not updated each time a file is created or deleted, the inode counts from the ZFILE df display should only be used as estimates of the in-use and available inodes. If one processor creates or deletes a large number of files, the changes to the inode counts are not reflected on every processor in the loosely coupled complex. As a result, the ZFILE df command might display significantly skewed inode counts on different processors. This Idea would provide a mechanism for the TFS to synchronize the inode counts across processors so that the ZFILE df display is more consistent.