recover standby database from service 如何操作
时间: 2023-11-27 12:50:32 浏览: 36
要恢复一个 standby 数据库,您需要以下步骤:
1. 确保您已经将服务连接到 standby 数据库上。
2. 检查 standby 数据库的状态。您可以使用以下命令:
```
SELECT NAME, OPEN_MODE, DATABASE_ROLE FROM V$DATABASE;
```
如果数据库的角色为 STANDBY,则表示它是一个 standby 数据库。
3. 将 standby 数据库关闭。您可以使用以下命令:
```
SHUTDOWN IMMEDIATE;
```
4. 将 standby 数据库转换为可写模式。您可以使用以下命令:
```
STARTUP MOUNT;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
ALTER DATABASE OPEN;
ALTER DATABASE CONVERT TO PRIMARY;
```
5. 确认 standby 数据库已经转换为可写模式。您可以使用以下命令:
```
SELECT NAME, OPEN_MODE, DATABASE_ROLE FROM V$DATABASE;
```
6. 现在您可以在此数据库上执行所需的操作。请注意,这个数据库不再是一个 standby 数据库,而是一个 primary 数据库。完成操作后,您可以将其转换回 standby 模式,以便它可以继续接收来自 primary 数据库的 redo 数据。
相关问题
recover standby database from service
To recover a standby database from a service, you can follow the below steps:
1. Connect to the primary database using SQL*Plus or any other database client tool.
2. Check the status of the standby database using the following command:
```
SELECT NAME, DB_UNIQUE_NAME, DATABASE_ROLE, OPEN_MODE FROM V$DATABASE;
```
This command will display the name, unique name, database role, and open mode of the primary and standby databases.
3. If the standby database is not in sync with the primary database, you need to perform a switchover to make it the primary database.
4. Once the standby database is in sync with the primary database, you can start the recovery process by executing the following command:
```
RECOVER DATABASE USING SERVICE '<service_name>';
```
This command will initiate the recovery process on the standby database using the specified service name.
5. Monitor the progress of the recovery process using the following command:
```
SELECT PROCESS, SEQUENCE#, BLOCK#, STATUS FROM V$MANAGED_STANDBY;
```
This command will display the current status of the recovery process.
6. Once the recovery process is complete, you can open the standby database in read-only mode using the following command:
```
ALTER DATABASE OPEN READ ONLY;
```
This command will allow you to access the standby database in read-only mode.
Note: Make sure to maintain proper backups of both the primary and standby databases to avoid any data loss.
ECDSA.recover
ECDSA.recover is a function in the ECDSA (Elliptic Curve Digital Signature Algorithm) cryptographic system that allows a user to recover the public key from a given signature and message. This function is useful in situations where the public key is unknown but the signature and message are available.
The ECDSA algorithm involves three steps: key generation, signature generation, and signature verification. In the key generation step, a private key is generated using a random number generator, and the corresponding public key is derived from the private key. In the signature generation step, a message is hashed and signed using the private key to generate a signature. In the signature verification step, the signature is verified using the public key to ensure that it was generated by the owner of the private key.
In some cases, the public key may not be available, but the signature and message are known. In such cases, the ECDSA.recover function can be used to recover the public key from the signature and message. The function takes three inputs: the message, the signature, and the recovery parameter. The recovery parameter is a number between 0 and 3 that specifies which of the four possible public keys should be recovered from the signature. Once the public key is recovered, it can be used to verify the signature and authenticate the message.
Overall, ECDSA.recover is a useful function in the ECDSA cryptographic system that allows for public key recovery in situations where it is unknown but the signature and message are available.