单项选择题
The user SCOTT executes the following command successfully to increase the salary values in one of his sessions：
SQL> UPDATE emp SET sal=sal*1.15 WHERE deptno=20;
Before SCOTT ends the transaction， user HR who has the privileges on EMP table executes a query to fetch the salary details but finds the old salary values instead of the increased values.
Why does HR still see the old data？（）
A.because of redo data from redo log file
B.because of data from database buffer cache
C.because of data from a temporary tablespace
D.because of undo data from the undo tablespace
相关考题
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单项选择题
Your database is running under automatic undo management and the UNDO_RETENTION parameter is set to 900 sec. You executed the following command to enable retention guarantee： SQL> ALTER TABLESPACE undotbs1 RETENTION GUARANTEE What effect would this statement have on the database？（）
A.The extents in undo tablespace retain data until the next full database backup.
B.The extents containing committed data in the undo tablespace are never overwritten.
C.The extents which no longer contain uncommitted data in the undo tablespace are not overwritten for at least15 minutes.
D.The extents containing committed data in the undo tablespace are not overwritten until the instance is shut down. -
多项选择题
A user receives the following error while executing a query： ORA01555：snapshot too old Which two options can be the solutions to avoid such errors in future？（）
A.increase the size of redo log files
B.increase the size of the undo tablespace
C.increase the size of the Database Buffer Cache
D.increase the size of the default temporary tablespace
E.enable the retention guarantee for the undo tablespace -
多项选择题
User SCOTT executes the following command on the EMP table but has not issued COMMIT， ROLLBACK，or any data definition language （DDL） command： SQL> SELECT job FROM emp 2 WHERE job=’CLERK’ FOR UPDATE OF empno SCOTT has opened another session to work with the database. Which three operations would wait when issued in SCOTT’s second session？（）
A.LOCK TABLE emp IN SHARE MODE;
B.LOCK TABLE emp IN EXCLUSIVE MODE;
C.DELETE FROM emp WHERE job=’MANAGER’;
D.INSERT INTO emp（empno，ename） VALUES （1289，’Dick’）;
E.SELECT job FROM emp WHERE job=’CLERK’ FOR UPDATE OF empno;
