09/26/96,
 
  Common Questions Related to Databases and Disk Space
 
 
 
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  ABOUT THIS DOCUMENT
 
       This document contains common questions related to databases
       and disk space and is applicable to AIX 3.2 and 4.1.
 
  QUESTIONS AND ANSWERS
 
       Q1.       Why don't I see more free blocks with "df" when I
                 remove a large Oracle file with "rm"?  (The ques-
                 tion could also be for non-database files.)
 
       A1.       The most common reason for this is that the file
                 is still open by some other process(es).  Look at
                 which process(es) are using the file with "fuser
                 -u <filename>" and make sure they stop using the
                 file. "fuser -k <filename>" will kill all such
                 processes.  Only then will you see the data blocks
                 associated with that file released. This is true
                 of any Unix implementation because data blocks
                 associated with a file will be released only when
                 the reference count in the inode of that file is
                 0, implying that no process has that file open.
                 In the case of Oracle, just killing all processes
                 using that file might still not free the space.
 
       You might have to then do the following:
 
       1.  shutdown Oracle
 
       2.  kill all processes using the database files
 
       3.  run slibclean
 
       Q2.       Why do I see the "ls -l" output show me huge sizes
                 of Oracle files while "df" shows me many more free
                 blocks than what "ls -l" adds up to?
 
       A2.       Oracle creates sparse files (large empty files)
                 because that is the way they handle free space for
                 inserts into the table (apparently). As a result,
                 although the file might be of size 1Mb, if it has
                 just 10 characters written into it, it will occupy
                 just 1 data block (4Kb) in the filesystem.  Hence,
 
                 Common Questions Related to Databases and Disk Space  1
 
 
                                                               09/26/96,
 
                 "df" will show a lot more free blocks than you
                 would expect.
 
       For further information:
 
       1.  Request fax #2480 ("Why Numbers from "du -sk" and "df"
           Disagree") from 1-800-IBM-4FAX.
 
       2.  Request Hone item: HQ548438 from your IBM represen-
           tative.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                 Common Questions Related to Databases and Disk Space  2
 
 
                                                               09/26/96,
 
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  END OF DOCUMENT (oracle.krn)
 
 
 
                 Common Questions Related to Databases and Disk Space  3