Which two statements are true about transactions in Oracle Database 12c?
A.
Multiple transactions can use the same undo segment.
B.
A transaction is assigned an undo segment when it is started.
C.
Multiple transactions cannot share the same extent in an undo tablespace.
D.
If all the segments in an undo tablespace are used, transactions use system undo segments to
store undo data.
BC
AB
see https://docs.oracle.com/database/121/CNCPT/logical.htm#CNCPT305
“Undo Segments and Transactions”
AB
AB
I believe it should be A,C
A,B,C.. all 3 are correct.. refer to the below link-
https://docs.oracle.com/database/121/CNCPT/logical.htm#CNCPT305
A, B
not C:
At any given time, a transaction writes sequentially to only one extent in an undo segment, known as the current extent for the transaction. >>> Multiple active transactions can write simultaneously to the same current extent or to different current extents. << For me this means they can share an extent!
https://docs.oracle.com/database/121/CNCPT/logical.htm#CNCPT305
A : When a transaction starts, the database binds (assigns) the transaction to an undo segment
B : Multiple active transactions can write concurrently to the same undo segment or to different segments
refer : https://docs.oracle.com/database/121/CNCPT/logical.htm#CNCPT305
Sorry it’s Vice versa :
B : When a transaction starts, the database binds (assigns) the transaction to an undo segment
A : Multiple active transactions can write concurrently to the same undo segment or to different segments