IBM Mainframe Forum

In a db2-Cobol program with restart logic, I have defined a Cursor to select & Update rows as below -





Depending on the values of COL_L, COL_M, COL_N, COL_O, I’ll update certain values to COL_X and COL_Y

Note: ONLY COL_A & COL_B in WHERE clause are part of INDEX of TABLE_1

Question:
1. Since I didn’t use ORDER BY clause, will the program fetches the data in the same order in the two different runs (- given that there are no inserts or deletes between two runs)?
2. How does row positioned cursor works – On what basis 1st row is selected from the resultant table?

Q1 - what happened when you tried it

yes,I did a test run(s) with 100 records as input and got positive results. Data was processed in the same order.

But the final production run will be against 70 million rows, So I wanted to make sure it works in all cases and understand how row positioned cursor works (Pointing the 1st row and order).
For this I tried reffering IBM knowledge centre, where it was stated -

When your program issues a row-positioned FETCH statement, Db2 uses the cursor to point to a row in the result table, making it the current row. Db2 then moves the current row contents into the program host variables that you specified in the INTO clause of the FETCH statement.

https://www.ibm.com/support/knowledgecenter/en/SSEPEK_11.0.0/intro/src/tpc/db2z_rowretrievalwithcursor.html

Since I didn’t use ORDER BY clause, will the program fetches the data in the same order in the two different runs (- given that there are no inserts or deletes between two runs)?

Not guaranteed. The database could have changed in other ways - reorganised, moved to different volume etc. The only guarantee is when you use the ORDER BY clause.