My SAP back end db is db2. Need to understand the impact on this running database (db2 under HPUX) if I change the OS date and set it to a past date please.
That's an extremeley broad question. If your DB's tables use date in the primary keys you could run into duplicate problems. If you query by date range you may have duplicates or holes in your data. You may even have difficulty saying which row was written before another, depending on your design. Reproducing any previous state may become impossible e.g. "What was the customer's balance on the 1st January?" and so forth.
Really, you need to understand your application and DB design deeply, and test, test, test.
The DB2 for LUW reference does have a section under high availability entitled "Scenario: Changing the system clock" which goes through the implication of moving the system clock forwards or backwards. It is specifically to do with HADR (high availability), but it's worth a look anyway (it's also worth noting that it's talking about moving the clock back minutes, not days).
Moving the clock forwards is never a problem. Moving the clock backward can cause several issues:
CURRENT TIMESTAMPin a query or manipulation statement (or column default) will potentially break
I would be quite surprised if a SAP installation wasn't using archived logging (even though it's not the default in DB2), so I would expect that last point would apply. You can check by looking at the database configuration (
GET DB CFG FOR <dbname>) to see whether
LOGARCHMETH1 is something other than
To summarize: the fact it breaks point in time recovery is particularly scary and should serve as a giant warning sign that this shouldn't be done unless absolutely required.