单项选择题 You executed the following command to perform a backup of the USERS tablespace：SQL> ALTER TABLESPACE users BEGIN BACKUP；ALTER TABLESPACE users BEGIN BACKUP* ERROR at line 1： ORA-01123： cannot start online backup； media recovery not enabled What could be the reason for this error（）

单项选择题 The TRANS_SUMMARY table contains product-wise transaction details that get updated with every transactionin the system. Each row has cumulative transaction details of a single product and every product is identified bya product code， which is the primary key.As part of the archival process， the company wants to transfer therows in the TRANS_SUMMARY table to the TRANS_SUMMARY_DUP table at the end of every quarter of theyear. Along with existing products， the company deals with many new products during every quarter. Whichmethod is best suited for this quarterly data transfer（）

多项选择题 Whichtwostatementsaboutthebackgroundprocessofthedatabasewriteraretrue（）