Dear Subhadeep,
Please note AS91 will not post any entries to FI-GL. Only asset sub ledger balances are being updated.
In order to tally FI-GL and FI-AA
You have different options
OASV - If you are before go live, you can use this, there is no need to use OAMK to reset the reconciliation accounts in your company code. However, after go live you are not supposed to use this, as you might have changed your company code status.
ABF1 - You can post the journal on your reconciliation accounts by using posting keys 70 and 75
F-02 - Simple Journal, however, you need to use OAMK to post the journal. Once you post the journal you need to put it back in OAMK.
Once you ensure that you posted right entries, please run ABST2 and ABST and see if there are any differences. If you believe, there are some differences then post OASV Journal as stated above.
Ultimate aim is you should not see any differences in ABST2
Hope this helps you.
Regards,
Ravi