Which two statements are true regarding transactions in an Oracle database（） ["Multiple transactions can use the same undo segment.","A transaction is assigned an undo segment when it is started.","More than one transaction cannot share the same extent in the undo tablespace.","The transactions use system undo segment to store undo data if all the segments in the undo tablespaceare used."]
在基于用例的面向对象分析过程中，定义交互行为的关键在于通过描述分析类实例之间的（）将用例的职责分配到分析类中。 ["消息传递","关联关系","继承关系","上下文关系"]
You need to resolve the blocking issue that is affecting the performance of the CRM system. What should you do?（） ["Replace the named query with an SQL view.","Set the transaction isolation level to serializable in the named query.","Set the source database to use snapshot isolation.","Set the transaction isolation level to repeatable read in the named query."]
You are a professional level SQL Server 2005 database administrator in an international corporation named Wiikigo. You are experienced in implementing high-availability solutions， monitoring the database server， and design deployment. In the company， you major job is the deployment， maintenance and support of Microsoft SQL Server 2005. You work as the administrator of a SQL Server 2005 computer， and the computer is named SQL1. Microsoft Windows Server 2003 is run by all servers. All the servers belong to a Microsoft Active Directory domain. According to the company written security policy， strong passwords are mandated for all domain， local， and application accounts. The company utilizes a Group Policy object （GPO） to deploy the proper domain password policy. MS-DOS-based or UNIX-based operating systems are run by many of the company’s computers. Varying levels of access to a database named Services on SQL1 is requested by the computers. Since you are the database administrator， you are required to confirm that the Services database can be accessed by these computers. And the company’s written security policy should not be violated. Which action should be performed by you？（） ["A domain account should be created for each of the company’s users. And then， each domain account should be offered with access to SQL1 and the Services database.","A local logon account should be created on SQL1 for each of the company’s users. And then， each logon account should be offered with access to SQL1 and the Services database.","One SQL Server logon account should be created for all of the company’s computers running MS-DOS or UNIX-based operating systems. And then， the Enforce password policy option should be enabled for users’ accounts. At last， the logon accounts should be provided with access to the Services database.","A SQL Server logon account should be created for each of the company’s users. And then， the Enforce password policy option should be enabled for each logon account. At last， each logon account should be offered with access to the Services database.","A virtual directory should be configured through Internet Information Services （IIS） for access to SQL1. And then， users should be directed to the virtual directory for data access."]
土壤、地形条件在草地形成中的主要作用是如何体现的。
偏航制动器的作用是什么？
