How to find out which member a row exists?

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You can use the DBPARTITIONNUM scalar function to find out which member a row exists.

Example 1:  Find out which member a row with EMPNO='000050' exists:
$ db2 "select dbpartitionnum(EMPNO) partition_number from employee where EMPNO='000050'"

PARTITION_NUMBER
----------------
               3

Example 2:  Find out the member on which MICHAEL THOMPSON's employee data is stored:
 db2 "select dbpartitionnum(EMPNO) partition_number from employee where FIRSTNME='MICHAEL' and LASTNAME='THOMPSON'"

PARTITION_NUMBER
----------------
               1

Example 3:  Find out the row count for each member, you can use this result to check whether the data distribution is even or skew:
$ db2 "select dbpartitionnum(EMPNO) partition_number,count(*) as row_count from employee group by dbpartitionnum(EMPNO) order by dbpartitionnum(EMPNO)"

PARTITION_NUMBER ROW_COUNT
---------------- -----------
               0           4
               1           9
               2          11
               3           9
               4           9

Note: 1. All above using the sample database to demonstrate. db2nodes.cfg used:
0 host1 0
1 host1 1
2 host1 2
3 host2 0
4 host2 1

           2. Instead of EMPNO, you can specify any column name of EMPLOYEE to DBPARTITIONNUM function, the result should be the same.