2) May i know the impact of settlement? Why do we need to do it? I don't see in change/message post execution of settlement.
You can check if you need to make Settlement of your transaction at "Status" tab.
If you have Processing category - 0002 with settlement - then you have to do settlement.
If you have - 0001 without settlement - you don't have to make it.
What settlement means - in general - if you have processing category "0002 With settlement" - you create transaction and all data inside transaction is Planned data. You can't make posting with TBB1 befor you make settlement. You can agree all transaction data with banks and your colleguaes. When all data agreed, then you make settlement and the data becomes Fact data. And only then it is possible to make postings with TBB1.
You can change processing category here: IMG -> Financial Supply Chain Management -> Treasury and Risk Management -> Transaction Manager -> Money Market -> Transaction Management -> Transaction Types -> Define Transaction Types
3) System doesn't post accounting documents or not showing any output in t.code-TBB1 for facility( product type-56B) or interest instrument (product type-55A).what time books will be updated?
I think it's because you have Processing category "0002 with settlement" as i described above.
1) Can we restrict user not to post greater than the credit line ?
The credit line or subline with limits is resctricting from posting greater than the credit line.
But sometimes we have only warning error and it allows us to make postings.
The description of this error have the solution
You can press "Change message control" line or run OBA5 transaction. Don't forget to copy Message number. The structure of message number is: the last three digits is message number, the res is Application area:
Enter FTR_ASSIGNMENT in application area.
Then enter message number 003 and change Active message type to E (error) in Online and Batch.
Then if you exceed the credit line or tranche you'll have error which will stop you from creating transaction with amount greater than credi line
