Understanding the ARSRES table

[Trambak]

Hello
I have been going through the ARSRES table was surprised with the entries. Can someone please let me know what each of these scenarios mean? How is it possible to have an entry without an ADD_DATE? What does the ADD_DATE signify?

SCENARIO 1:
$ db2 "select * from root.arsres where root.arsres.ADD_DATE is null FETCH FIRST 2 ROWS ONLY"

Code: [Select]

RID         AGID        PRI_NID SEC_NID COMP_TYPE             ADD_DATE             COMP_SIZE   DECOMP_SIZE EXP_DATE             HOLD
----------- ----------- ------- ------- --------------------- -------------------- ----------- ----------- -------------------- ------
          2         642       2       0 x'5A'                                    -           -           -                    -      -
          3         642       6       0 x'5A'                                    -           -           -                    -      -

SCENARIO2:
$ db2 "select * from root.arsres where root.arsres.EXP_DATE is null FETCH FIRST 2 ROWS ONLY"

Code: [Select]

RID         AGID        PRI_NID SEC_NID COMP_TYPE             ADD_DATE             COMP_SIZE   DECOMP_SIZE EXP_DATE             HOLD
----------- ----------- ------- ------- --------------------- -------------------- ----------- ----------- -------------------- ------
          2         642       2       0 x'5A'                                    -           -           -                    -      -
          3         642       6       0 x'5A'                                    -           -           -                    -      -

SCENARIO:3
$ db2 "select * from root.arsres where root.arsres.EXP_DATE is null and root.arsres.ADD_DATE is not null FETCH FIRST 2 ROWS ONLY"

Code: [Select]

RID         AGID        PRI_NID SEC_NID COMP_TYPE             ADD_DATE             COMP_SIZE   DECOMP_SIZE EXP_DATE             HOLD
----------- ----------- ------- ------- --------------------- -------------------- ----------- ----------- -------------------- ------
      38424         801       8       0 x'4F'                           1033813294           -           -                    -      -
      38425         801       8       0 x'4F'                           1033813314           -           -                    -      -


Edit:  Added fixed-width formatting for readability.

[Trambak]

Also I would like to understand how does CMOD calculate the EXP_DATE in the table and what does it correspond to? I have not able to find a suitable relation between the ADD_DATE and EXP_DATE.