ora-12516, tns:listener could

ORA-12516是Oracle数据库的一个错误代码，表示TNS监听程序无法处理当前的连接请求。这通常是由于监听程序已经达到了其最大连接数限制，无法再处理新的连接请求所致。要解决这个问题，可以通过增加监听程序的最大连接数限制或者优化数据库连接池的使用来缓解这个问题。

相关问题

ORA-12516, TNS:listener could not find available handler with matching protocol stack

This error message typically indicates that the Oracle listener process is unable to establish a connection to a database instance. There may be several causes for this issue, including:

1. Insufficient resources: The listener process may not have enough available resources to handle incoming connections. This could be due to limited system resources or heavy load on the server.

2. Database instance not available: The database instance that the listener is trying to connect to may not be available or may have been shut down.

3. Incorrect configuration: The listener configuration may be incorrect, preventing it from properly connecting to the database instance.

To resolve this issue, you can try the following steps:

1. Increase resources: If the issue is due to insufficient resources, you can try increasing the available resources on the server.

2. Check database availability: Verify that the database instance is available and running.

3. Check listener configuration: Verify that the listener configuration is correct and that it is able to connect to the database instance.

4. Restart listener: If all else fails, try restarting the listener process and see if that resolves the issue.

ORA-12154：TNS:could not resolve the connect identifier specified

ORA-12154错误是Oracle数据库中的一种网络连接错误，通常出现在尝试通过TNS (Transparent Network Substrate) 连接到数据库服务时。这个错误意味着系统无法解析你提供的连接标识符，可能是服务名、主机名、端口号或者是SID (System Identifier)。

具体原因可能有：
1. **配置文件问题**：TNSnames.ora 或 listener.ora 文件中指定的连接信息可能存在错误，比如服务名未正确配置。
2. **网络连通性**：客户端与数据库服务器之间的网络不通，或者防火墙阻止了连接请求。
3. **服务未启动**：如果数据库服务未正常运行，也可能导致此错误。
4. **权限限制**：用户可能没有足够的权限来连接到特定的服务。

解决这个问题需要检查并修复上述可能的原因：
1. 检查TNSnames.ora文件中的连接描述是否匹配实际的数据库设置。
2. 确保网络环境畅通无阻，并确认防火墙设置允许连接。
3. 启动数据库服务并且验证用户是否有正确的连接权限。
4. 如果是远程连接，确认是否开启了监听器和listener.ora文件中的LISTENER参数。