Comments on the 2017-autumn examination of the real problem-operation engineer A_ operation and maintenance of the basic

1, the database index can significantly improve the efficiency of which operation.
Correct answer: A

A SELECT

B INSERT into ... VALUES ...

C UPDATE

D DELETE

2. Database: Which of the following locking mode can provide the best parallel access performance.
Correct answer: D

Column A Lock

Table B Lock

Block C Lock

Line D Lock

3. Omit the WHERE clause from the DELETE statement, and what will happen.
Correct answer: B

A DELETE statement will fail because no records can be deleted

The B DELETE statement deletes all records from the table

The C DELETE statement prompts the user to enter the deleted criteria

The D DELETE statement will fail because of a syntax error

4, raceroute commonly used is what kind of network layer protocol.
Correct answer: D

A VRRP

B UDP

C ARP

D ICMP

5. Which LSA in the OSPF protocol can only propagate within the region.
Correct answer: A

A 2

B 3

C 5

D 7

6, in the Linux system, which of the following signals can not be captured.
Correct answer: B

A Sighup

B SIGKILL

C Sigquit

D SIGUSR1

7, Linux, how to see how a port is occupied by what process.
Correct answer: B

A Netstat-an|grep Port number

B NETSTAT-TNLP | grep Port number

C Iostat-an | grep Port number

D IOSTAT-DXT | grep Port number

8, the list how to remove the duplicate elements.
Correct answer: B

A list can't go heavy

B first converts the list to a heavy set and then the list

C first converts the list to a heavy tuple, and then in the list

D list will not have duplicates

9, what is the difference between a list of Python and a tuple (Tuple).
Correct answer: A

A list is mutable and the tuple is not variable

B No difference

C limit is not the same

D lists can be iterated, tuples cannot iterate

10. The right thing to say about the inheritance of the Python class is.
Correct answer: C

A Python class cannot inherit

B can inherit however, the constructor of the parent class cannot be executed

C can have multiple parent classes

D can only have one parent class

11, the following about the description of the port which is correct.
Correct answer: A B C D

A FTP uses TCP 20 port

B FTP uses TCP 21 port

C DNS uses TCP 53 ports

D DNS uses UDP 53 ports

12, the following about the HTTP protocol and the difference between get and POST methods, which are wrong.
Correct answer: A C

A They can all be collected and cached

The B Get request parameter is placed in the URL

C get is used only for query requests and cannot be used for request data

D get should not handle requests for sensitive data

13, a simple Web site may consist of these three parts: a Web server (providing Web pages and HTTP services), a background server (such as Java background Program, responsible for computing), a MySQL database server (store user data). However, we know that such a Web site is also very fragile, any of the above three server problems (server problems, or server network problems, or running the above program problems), will cause the site can not be accessed. Obviously this is not in line with the United States and the general public reviews to the user's service commitment. Now, assuming you are the technical manager of the company, what kind of reinforcement or improvement work do you think you will do to help improve the usability of the site for the above 3 parts? (as many lists as possible)

The main means are redundant backups of data and services and failover

Load balancing and so on.

14, from which several aspects to evaluate a hash function is good or bad. Enumerates a few common hash functions.
Reference Answer:

Standard for judging the hash function

1. Efficient, save CPU, in order to improve concurrency, as the middle layer, the need for efficient based on key to compute the hash

2. Conflict as small as possible to create a unique index

3. Save as much space as possible. For example, to store this result in a database and index the result of the hash, we want the column to be as small as possible in order to save data storage space. Especially when the database is indexed, the fields that are indexed are naturally smaller and better.

4. To even, especially when there are multiple nodes, to ensure the distribution of each key evenly, more important, otherwise the load can not be balanced

5.rehash, to ensure that the key redistribution as small as possible to avoid the rear end of the larger impact

Common hash functions such as MD5,SHA-1,CRC16,CRC32, etc.