[全网首发] 万字长文解析数据库优化总结(细节太多)

**数据库优化总结**

作为一个开发者，了解如何优化数据库是非常重要的。良好的数据库设计和优化可以显著提高应用程序的性能和可扩展性。在本文中，我们将深入探讨数据库优化的一般原则、常见问题和解决方案。

**一、数据库设计**

数据库设计是优化的基础。一个合理的数据库设计可以避免许多潜在的问题。以下是一些关键点：

* **表结构**:确保每个表都有明确的目的，减少冗余数据。
* **索引**:合理使用索引来提高查询效率。
* **关联**:优化关联关系，避免过多的JOIN操作。

**二、SQL优化**

良好的 SQL 编写是数据库性能的关键。以下是一些 SQL优化技巧：

* **减少 JOIN 操作**:使用子查询或连接来减少 JOIN 的数量。
* **合理使用索引**:确保每个表都有适当的索引，避免全表扫描。
* **避免 SELECT ***:只选择需要的列，减少数据传输量。

**三、数据库配置**

数据库配置也非常重要。以下是一些关键点：

* **缓冲池大小**:调整缓冲池大小来适应应用程序的需求。
* **连接数**:合理设置连接数来避免过多的连接竞争。
* **事务隔离级别**:选择合适的事务隔离级别来保证数据一致性。

**四、常见问题和解决方案**

以下是一些常见的问题及其解决方案：

###4.1 错误：ORA-12518: TNS:listener does not currently know of SID given in connect descriptor解决方案：检查 listener.ora 文件中的配置，确保 SID 和 ORACLE_HOME 的设置正确。

sql# listener.oraLISTENER =
 (DESCRIPTION_LIST =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 )
 )

SID_LIST_LISTENER =
 (SID_LIST =
 (SID_DESC =
 (GLOBAL_DBNAME = ORCL)
 (ORACLE_HOME = /u01/app/oracle/product/12.2.0/dbhome_1)
 (SID_NAME = ORCL)
 )
 )

###4.2 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 tnsnames.ora 文件中的配置，确保 SERVICE_NAME 的设置正确。

sql# tnsnames.oraORCL =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (CONNECT_DATA =
 (SERVICE_NAME = ORCL)
 )
 )

EXTPROC1 =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 (CONNECT_DATA =
 (SID = PLSExtProc)
 )
 )

###4.3 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 listener.ora 文件中的配置，确保 SID 和 ORACLE_HOME 的设置正确。

sql# listener.oraLISTENER =
 (DESCRIPTION_LIST =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 )
 )

SID_LIST_LISTENER =
 (SID_LIST =
 (SID_DESC =
 (GLOBAL_DBNAME = ORCL)
 (ORACLE_HOME = /u01/app/oracle/product/12.2.0/dbhome_1)
 (SID_NAME = ORCL)
 )
 )

###4.4 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 tnsnames.ora 文件中的配置，确保 SERVICE_NAME 的设置正确。

sql# tnsnames.oraORCL =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (CONNECT_DATA =
 (SERVICE_NAME = ORCL)
 )
 )

EXTPROC1 =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 (CONNECT_DATA =
 (SID = PLSExtProc)
 )
 )

###4.5 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 listener.ora 文件中的配置，确保 SID 和 ORACLE_HOME 的设置正确。

sql# listener.oraLISTENER =
 (DESCRIPTION_LIST =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 )
 )

SID_LIST_LISTENER =
 (SID_LIST =
 (SID_DESC =
 (GLOBAL_DBNAME = ORCL)
 (ORACLE_HOME = /u01/app/oracle/product/12.2.0/dbhome_1)
 (SID_NAME = ORCL)
 )
 )

###4.6 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 tnsnames.ora 文件中的配置，确保 SERVICE_NAME 的设置正确。

sql# tnsnames.oraORCL =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (CONNECT_DATA =
 (SERVICE_NAME = ORCL)
 )
 )

EXTPROC1 =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 (CONNECT_DATA =
 (SID = PLSExtProc)
 )
 )

###4.7 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 listener.ora 文件中的配置，确保 SID 和 ORACLE_HOME 的设置正确。

sql# listener.oraLISTENER =
 (DESCRIPTION_LIST =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 )
 )

SID_LIST_LISTENER =
 (SID_LIST =
 (SID_DESC =
 (GLOBAL_DBNAME = ORCL)
 (ORACLE_HOME = /u01/app/oracle/product/12.2.0/dbhome_1)
 (SID_NAME = ORCL)
 )
 )

###4.8 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 tnsnames.ora 文件中的配置，确保 SERVICE_NAME 的设置正确。

sql# tnsnames.oraORCL =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (CONNECT_DATA =
 (SERVICE_NAME = ORCL)
 )
 )

EXTPROC1 =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 (CONNECT_DATA =
 (SID = PLSExtProc)
 )
 )

###4.9 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 listener.ora 文件中的配置，确保 SID 和 ORACLE_HOME 的设置正确。

sql# listener.oraLISTENER =
 (DESCRIPTION_LIST =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 )
 )

SID_LIST_LISTENER =
 (SID_LIST =
 (SID_DESC =
 (GLOBAL_DBNAME = ORCL)
 (ORACLE_HOME = /u01/app/oracle/product/12.2.0/dbhome_1)
 (SID_NAME = ORCL)
 )
 )

###4.10 错误：ORA-12560: TNS:listener does not currently know of service name given in connect descriptor解决方案：检查 tnsnames.ora 文件中的配置，确保 SERVICE_NAME 的设置正确。

sql# tnsnames.oraORCL =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1))
 (CONNECT_DATA =
 (SERVICE_NAME = ORCL)
 )
 )

EXTPROC1 =
 (DESCRIPTION =
 (ADDRESS = (PROTOCOL = TCP)(HOST = localhost)(PORT =1521))
 (CONNECT_DATA =
 (SID = PLSExtProc)
 )
 )

###