“HOLD MEMO DR” is identical to “HOLD REL MEM CR”. Per our other article, HOLD REL MEM CR, it means there’s a large deposit pending credit to the account, which means it needs extra time to process the amount.
Typically, a portion of the large deposit should still be available for use though.
If you use Chase Bank and want more details, call their Deposit Hold Team at 877-691-808 (Press Option 1).