Oracle issue excerpt

1. Explain the differences between cold backup and hot backup and their respective advantages: Hot Backup is used to back up a database in archive mode when the database is still working. 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 database. 3. How to convert init. ora to spfile? Answer: Use 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.) Answer: data block is the smallest logical storage unit in the database. When database objects require more physical storage space, continuous data blocks constitute extent. all extents owned by a database object are called the segment of this object. 5. solution: 1. DESCRIBE command 2. DBMS_METADATA.GET_DDL Package 6. alert log. 7. comparison of the truncate and delete commands: both 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. how to use indexes: quick access to data block 9 in a table. the two types of tables in star schema and their respective data solutions are provided: Fact tables and dimension tables. fact table contains a large amount of main information, while dimension tables stores information about certain attribute descriptions of fact table. 10. what indexes should be created on the FACT Table? Q: bitmap index 11. Are there two constraints? Answer: primary key and foreign key 12. how to Create a parent table without affecting the sub-table? Answer: The foreign key of the sub-table is forced to be effective, the parent table is rebuilt, and the foreign key is activated 13. explanation of differences between archive and non-archive modes and their respective advantages and disadvantages answer: Archive Mode means that you can back up all the databases transactions and restore them 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? Q: Alter database backup control file to trace. 15. How many statuses have the database experienced during normal start? Answer: startup nomount-start startup mount of the database instance-database load startup open-OPEN Database 16. Which column can be used to distinguish between V $ view and GV $ view? A: INST_ID indicates a specific instance in the cluster environment. 17. How to generate an explain plan? A: Run utlxplan. SQL. create a plan table for specific SQL statements and run utlxplp using the explain plan set statement_id = 'tst1' into plan_table. SQL or utlxpls. check the SQL statement in the explain plan 18. how to increase the buffer cache hit rate? Q: When the database is busy, the buffer cache advisory tool is used to query v $ db_cache_advice. If necessary, you can use the alter system set db_cache_size command 19. How to handle the ORA-01555? 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? A: ORACLE_BASE is the root directory of oracle and ORACLE_HOME is the directory of oracle products. Author benitoro