簡單理解，UPDATE是一個先delete然後insert的一個符合操作，所以update後record的位置變化取決於insert的機制。
對於UPDATE操作，如果record長度沒有發生變化或者長度變短 ，record在page內的位置不會發生變化；如果長度增加 ：1.如果當前所在page的剩餘空間可以容下增加後的長度，那麼其他record向前移動回收空間，這條record放在所有記錄的後面。2.如果當前所在page的空間不能容下增加後的長度，DB2會就近尋找空間（向前或者向後16個page），如果沒有找到就做整個tablespace(partition)的掃描，如果依然沒能找到，就會extend這個tablespace(partition)，將記錄放在最末。
下面是做過的一些實驗，可以幫助理解上面的結論。
Case 1: Update record 1 and set varchar field from 0 length to 80 bytes (page has sufficient space to hold extended record)
Result: Row 1 moved to the end of the page, and other records are shifted to occupy the record 1's space. All records' page offset not changed.
Case 2: Update record 2 and set varchar field from 0 length to 80 bytes (page hasn't sufficient space to hold extended record)
Result: Record 2 moved to the last page of the table space(partition), new page offset assigned. The original record 2 is overwritten with a pointer to the last page and the new offset, record 2's space is not reallocated.
Case 3: Update record 3 and set varchar field from 0 length to 80 bytes
Result: Record 2's space is reallocated, record 3 moved to the end of the page(after record 1), all other records shifted up. Page offset not changed.
Case 4: Update record 4 and set char field from '0' to '1' (length not changed)
Result: Record 4's position is not changed, the record is updated as is.
Case 5: Update record 1 and set varchar field from '=========' to '--------' (length decreased)
(record 3 is at the bottom of the page, record 1 is before record 3)
Result: Record 1 is updated and position is not changed. The rest of the '===========' is not reallocated.
Case 6: Update record 1 and set varchar field from '---------' to '========' (length increased back to 80)
Result: Record 1 is moved to the end of the page, the records after record 1 are shifted up.
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Case 7: Delete record 118 from page 5 to make some free space (record 118 is the first record on page 5), then update record 4's varchar field on page 1 and increase the length to 80.
Result: After delete, the record 118 on page 5 is marked as free. Page header and last 4 bytes on the end of the page was changed.
After update, the space on the fifth page is reallocated, and all records shifted, the record 4 is appended to the end of the page, page offset is 0001. On the original location of record 4, a pointer is placed, pointing to record offset 1 on page 5.