Which two statements are true about undo segments and the use of undo by transactions in an Oracle database instance? (Choose two.)
Which two statements are true about undo segments and the use of undo by transactions in an Oracle database instance? (Choose two.)
Undo segments can extend when a transaction fills the last extent of the undo segment. Additionally, if there is no available undo tablespace when the database instance starts, undo segments can temporarily be stored in the SYSTEM tablespace, although this is not recommended.
1z0-082-question-64
maybe BDE ? BD from the 64 and E because "When the database instance starts, the database automatically selects the first available undo tablespace. If no undo tablespace is available, then the instance starts without an undo tablespace and stores undo records in the SYSTEM tablespace. This is not recommended, and an alert message is written to the alert log file to warn that the system is running without an undo tablespace."
I agree BD
A – false B – false; Undo wrap doesn't happen if a transaction needs an extra space within Undo. If you don't have space, you would see a message like can't extend Undo tablespace to XXX extents and the statement given would be aborted. Wrap, as Hemant has mentioned, would be for the inactive undo segments which are not in use now and can be re-used by the on-going transactions. https://forums.oracle.com/ords/apexds/post/why-does-undo-segment-wrap-around-4006 C – false; each transaction is assigned to only one undo segment, but an undo segment can service more than one transaction at a time; https://www.examtopics.com/discussions/oracle/view/26057-exam-1z0-082-topic-1-question-64-discussion/ D – true E – true; When the database instance starts, the database automatically selects the first available undo tablespace. If no undo tablespace is available, then the instance starts without an undo tablespace and stores undo records in the SYSTEM tablespace.
If there is no undo tablespace, undo segments can be stored in SYSTEM. And in question 64, people said "B wrong" in comments
D E perhaps !