[ADSM-L] TSM backup marked inactive

Here is the situation:
AIX 5.3
TSM 5.2
To a certain directory files are added daily and backed up (manual selective 
full backup:  dsmc backup file1)
A given file will never be backed up again
All files in this directory are kept on disk indefinitely
Each file has one and only one full backup in TSM
It has been my undestanding that as long as file is on disk, it will emain 
active in TSM
However, we are seeing that every day files backed up yesterday are marked 
inactive in TSM
Here is what it looks like
=> dsmc q ba -ina /D01/user01/REG15/SECT57/
IBM Tivoli Storage Manager
Command Line Backup/Archive Client Interface - Version 5, Release 2, Level 2.0
(c) Copyright by IBM Corporation and other(s) 1990, 2003. All Rights Reserved.

Node Name: NODE01
Session established with server TSM: AIX-RS/6000
  Server Version 5, Release 3, Level 0.0
  Server date/time: 06/27/12   22:49:45  Last access: 06/27/12   22:46:18

             Size      Backup Date        Mgmt Class A/I File
             ----      -----------        ---------- --- ----
   204,808,192  B  06/27/12   21:44:37    DEFAULT     A  
/D01/user01/REG15/SECT57/Z25147.TXT
    22,171,648  B  06/26/12   10:20:09    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25116.TXT
    33,841,152  B  06/26/12   10:20:13    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25117.TXT
    27,746,304  B  06/26/12   10:20:20    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25118.TXT
        12,288  B  06/26/12   10:20:25    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25119.TXT
   204,808,192  B  06/26/12   23:44:37    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25130.TXT
   204,808,192  B  06/26/12   23:44:56    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25131.TXT
   204,808,192  B  06/26/12   23:45:14    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25132.TXT
   115,646,464  B  06/27/12   01:44:38    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25133.TXT
        12,288  B  06/27/12   01:45:23    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25134.TXT
   204,808,192  B  06/27/12   03:44:38    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25135.TXT
   204,808,192  B  06/27/12   13:44:37    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25144.TXT
    40,316,928  B  06/27/12   14:36:38    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25145.TXT
     7,290,880  B  06/27/12   14:50:16    DEFAULT     I  
/D01/user01/REG15/SECT57/Z25146.TXT

Why are these files marked inactive?
Thanks in advance

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