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This article mainly explains "what are the questions and answers about oracle". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "what are the questions and answers about oracle"?

1. What dynamic performance views does oracle need to master?

Which dynamic performance views must be mastered in the daily management of Oracle database?

Answer: session class: v$session vposts processing SQL class: v$sql vposts qlarea; waiting class: vposts session sessions waitbook vadministrators systematical events.Lock: vlocations lockedobjects; backup classes: vposts rmanuals; hotspots: v$bh.

2. Tools for Oracle derivative to local excel

Hello, Mr. DBASK, there is no official data export tool, that is, input scripts, the results are directly output to the local excle.

Answer: the official sql developer tool can or use the SQLULDR2 in the tool download.

3. Does the replacement of Oracle rac public network equipment affect rac?

In the minicomputer with different deployment of the two zones, the two partition public networks are connected to different switches respectively, and the two switches will be replaced in turn by unplugging the original network cable and re-inserting it into the new switch. Will the operation status of rac be affected during the replacement process? Does rac need to restore operation after the network is restored?

Answer: if the IP and machine ENI remain unchanged, and only the replacement of the public network is involved, the cluster will not be affected. After the replacement, you only need to check whether the VIP of each node is normal (there is a problem of VIP drift in the replacement process).

4. Does OEM 13C support SMS alarm?

Does Oracle's OEM 13C support SMS alarm? Thank you!

Answer: you can call the script to send an alarm and encapsulate the SMS gateway in the script. In addition, you can encapsulate it in the email and then go to the SMS gateway. Refer to document 1662235.1.

5. Drop report ora-00054:resource busy

When I back up the drop table, I will report ora00054: resource busy and acquire with NOWAIT specified or timeout expired. I don't know if it has something to do with expdp

Answer: expdp will lock the object being exported. Drop needs to acquire exclusive locks. If there are other locks on the table, it will report to ora-54, check the locks in the database, or generate an ASH report at that time to view.

6. Ora-22992: cannot use the LOB locator selected from the remote table

Extract data from another database table through the data link, where a field data type in this table is of type clob, error ora-22992: the LOB locator selected from the remote table cannot be used.

Answer: the LOB field does not support DB LINK. You can create a temporary table by compromise, or materialize the view.

7. If the data is modified during expdp, will the updated data be synchronized? Do you allow ddl operations?

If the data is modified during expdp, will the updated data be synchronized? If you initiate an expdp task, you need to lock it. Are ddl operations not allowed during the job?

Answer: 1. Data that is updated after expdp is initiated will not be synchronized. The reason is to ensure data consistency. Extended knowledge: so when you use expdp to export data when the business is busy, you may encounter ORA-01555 errors. 2. It is not allowed, just like an insert table, it will be locked until it is submitted, and the DDL operation cannot be performed on the table. Most DDL needs exclusive locks, and 19c has some special cases.

8. DeadLock occurs in oracle9i

We use a kemp machine to balance the pressure of WEB applications. At 06:52 in the morning, deadLock suddenly appears. I want to know what causes this problem. I'm afraid there will be more of these problems later. Thank you.

Answer: the trace file shows clearly that it is caused by two transactions waiting for each other's modified records, which is closely related to the logic of the application and needs to be checked there: 1, avoid modifying the same records at the same time; 2, modify the records in the same order.

9. Can 10.2.0.4 be upgraded to 12.2.0.2?

Can you upgrade it directly, or do you need to upgrade to 11g before upgrading to 12.2?

Answer: 10204 cannot be upgraded directly to 12.2. you need to upgrade twice. Click the title to view the complete upgrade roadmap from 9i to 12.2.

10. Why is the session of update locking table in inactive state?

Database blocking, found that the source of the lock table is the update statement, but it is already in the inactive state, has not released the lock, does it take up resources?

Answer: it is normal for inactive not to release locks, see if the XID of vsession is not empty, or associate vtransaction according to taddr.

11. Whether the MySQL tablespace transfer export table will be locked

Tablespace transfer problem, for the table to be exported to perform the export operation, what if a business writes data at this time? I think the table should be locked at this time to write data report errors, but this will affect the business, how to do?

Answer: when using MyISAM as a storage engine, it does look like this. However, if the innodb storage engine is used, the full table scan does not affect writes.

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