DBA interview mode of Oracle Database

The following articles mainly introduce the example of Oracle Database DBA interview questions. This article describes the basic mode of Oracle Database DBA interview questions in a one-Answer manner, the following is an introduction to the related interview questions. I hope you will get some benefits.

1. Explain the differences between cold backup and hot backup and their respective advantages

Answer: Hot Backup is applicable to Oracle databases in archive mode. When the Oracle database is still working, it is backed up. Cold backup refers to the backup after the database is closed, applicable to all databases. The advantage of hot backup is that the database can still be used during Backup and can be restored to any point in time.

The advantage of cold backup is that its backup and recovery operations are quite simple, and because cold backup databases can work in non-archive mode, the database performance will be slightly better than the archive mode. Because archive log is not necessarily written to the hard disk)

2. You must use backup to restore the database, but you do not have control files. How can this problem be solved?

A: recreate the control file and use the recover command with the backup control file clause to restore the Oracle database.

3. How to convert init. ora to spfile?

Q: run the create spfile from pfile command.

4. Explain the differences between data block, extent, and segment. We recommend that you use an English term here)

A: data block is the smallest logical storage unit in the database. When an Oracle database object requires more physical storage space, the continuous data block forms extent. All extents owned by a database object are called the segment of this object.

5. Two Methods of checking table structure are provided.

Answer: 1. DESCRIBE command

2. DBMS_METADATA.GET_DDL package

6. How to view Oracle Database Engine errors

Answer: alert log.

7. Compare the truncate and delete commands

A: both of them can be used to delete all records in the table. The difference is that truncate is a DDL operation that moves HWK without rollback segment. Delete is a DML operation that requires rollback segment and takes a long time.

8. Reasons for using Indexes

A: quick access to the data block in a table

9. Two types of tables in star schema and their data are given respectively.

Answer: Fact tables and dimension tables. fact table contain a large amount of major information, while dimension tables stores information about certain attribute descriptions of fact table.

10. What indexes should be created on the FACT Table?

Answer: bitmap index)

11. are two related constraints provided?

Answer: primary key and foreign key

12. How to recreate a parent table without affecting the sub-table?

A: The foreign key of the sub-table is forced to take effect. The parent table is rebuilt and the foreign key is activated.

13. Explain the differences between archive and non-archive modes and their respective advantages and disadvantages

A: In archive mode, you can back up all Oracle database transactions and restore it to any point in time. Non-archive mode, on the contrary, cannot be recovered to any point in time. However, the non-archive mode can slightly improve the database performance.

14. How to Create a backup control file?

Answer: Alter database backup control file to trace.

15. How many statuses does the database normally start?

Answer:

Startup nomount-start a database instance

Startup mount-Database loading

Startup open-OPEN Oracle Database

16. Which column can be used to distinguish between the V $ view and the GV $ view?

A: INST_ID indicates a specific instance in the cluster environment.

17. How to generate an explain plan?

Answer:

Run utlxplan. SQL. Create a plan table for specific SQL statements and run utlxplp. SQL or utlxpls. SQL to view the explain plan

18. How to Increase the buffer cache hit rate?

A: When the database is busy, use the buffer cache advisory tool to query v $ db_cache_advice. If necessary, use the alter system set db_cache_size command.

19. How should ORA-01555 respond?

A: The specific error message is snapshot too old within rollback seg. Generally, you can increase the rollback seg to solve the problem. Of course, you also need to check the specific SQL text that causes the error.

20. What is the difference between $ ORACLE_HOME and $ ORACLE_BASE?

Answer: ORACLE_BASE is the root directory of oracle and ORACLE_HOME is the directory of oracle products.

21. How to determine the time zone of the Oracle database?

Answer: select dbtimezone from dual;

22. Explains the purpose of setting GLOBAL_NAMES to TRUE.

A: GLOBAL_NAMES indicates how to connect to the database. If this parameter is set to TRUE, you must use the same name to connect to the remote database when creating a database connection.

23. How to encrypt PL/SQL programs?

Answer: WRAP