1. 性能调优概述
Oracle数据库性能调优是数据库管理的重要组成部分，它涉及到SQL语句调优、索引调优、内存调优、存储调优和实例参数调优等多个方面。有效的性能调优可以提高数据库的响应速度，减少资源消耗，提高系统的整体性能。更多学习教程www.fgedu.net.cn
2. 性能监控
性能监控是性能调优的基础，通过监控可以发现性能瓶颈，为调优提供依据。
SELECT * FROM v$sysstat WHERE name IN (‘db block gets’, ‘consistent gets’, ‘physical reads’);NAME CLASS VALUE
——————————– ———- ———-
db block gets 1 12345
consistent gets 1 67890
physical reads 1 5678
— 查看会话性能指标
SELECT sid, username, status, machine, program
FROM v$session
WHERE status = ‘ACTIVE’;SID USERNAME STATUS MACHINE PROGRAM
———- —————————— ——– —————————— ——————————
1 SYS ACTIVE orcl sqlplus@orcl (TNS V1-V3)
— 查看SQL执行情况
SELECT sql_id, sql_text, executions, elapsed_time/1000000 AS elapsed_seconds
FROM v$sql
WHERE executions > 10
ORDER BY elapsed_seconds DESC;SQL_ID SQL_TEXT EXECUTIONS ELAPSED_SECONDS
————- —————————————- ———- —————
a1b2c3d4e5f6 SELECT * FROM employees WHERE department_id = :1 25 12.34
— 使用AWR报告
EXEC DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT();PL/SQL procedure successfully completed.
— 生成AWR报告
@$ORACLE_HOME/rdbms/admin/awrrpt.sql
— 使用ASH报告
@$ORACLE_HOME/rdbms/admin/ashrpt.sql
3. SQL语句调优
SQL语句调优是性能调优的核心，通过优化SQL语句可以显著提高数据库性能。
EXPLAIN PLAN FOR
SELECT * FROM employees WHERE department_id = 90;Explained.
SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY());PLAN_TABLE_OUTPUT
————————————————————————–
Plan hash value: 1445457117
————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
————————————————————————–
| 0 | SELECT STATEMENT | | 3 | 219 | 3 (0)| 00:00:01 |
|* 1 | TABLE ACCESS FULL| EMPLOYEES | 3 | 219 | 3 (0)| 00:00:01 |
————————————————————————–
Predicate Information (identified by operation id):
—————————————————
1 – filter(“DEPARTMENT_ID”=90)
— 创建索引
CREATE INDEX emp_dept_id_idx ON employees(department_id);Index created.
— 再次查看执行计划
EXPLAIN PLAN FOR
SELECT * FROM employees WHERE department_id = 90;Explained.
SELECT * FROM TABLE(DBMS_XPLAN.DISPLAY());PLAN_TABLE_OUTPUT
————————————————————————–
Plan hash value: 3956160932
————————————————————————–
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
————————————————————————–
| 0 | SELECT STATEMENT | | 3 | 219 | 2 (0)| 00:00:01 |
| 1 | INDEX RANGE SCAN| EMP_DEPT_ID_IDX| 3 | 219 | 2 (0)| 00:00:01 |
————————————————————————–
— 优化SQL语句
— 原始SQL
SELECT * FROM employees WHERE hire_date > ’01-JAN-2020′;– 优化后的SQL
SELECT employee_id, first_name, last_name, department_id
FROM employees
WHERE hire_date > TO_DATE(‘2020-01-01’, ‘YYYY-MM-DD’);– 使用绑定变量
DECLARE
v_dept_id NUMBER := 90;BEGIN
FOR rec IN (
SELECT * FROM employees WHERE department_id = v_dept_id
) LOOP
DBMS_OUTPUT.PUT_LINE(rec.first_name || ‘ ‘ || rec.last_name);END LOOP;END;/
4. 索引调优
索引调优是提高查询性能的重要手段，通过合理创建和使用索引可以显著提高查询速度。
SELECT index_name, table_name, uniqueness
FROM user_indexes
WHERE table_name = ‘EMPLOYEES’;INDEX_NAME TABLE_NAME UNIQUENESS
—————————— —————————— ———-
PK_EMPLOYEES EMPLOYEES UNIQUE
EMP_DEPT_ID_IDX EMPLOYEES NONUNIQUE
— 查看索引列
SELECT index_name, column_name, column_position
FROM user_ind_columns
WHERE table_name = ‘EMPLOYEES’;INDEX_NAME COLUMN_NAME COLUMN_POSITION
—————————— ——————– ——————
PK_EMPLOYEES EMPLOYEE_ID 1
EMP_DEPT_ID_IDX DEPARTMENT_ID 1
— 创建复合索引
CREATE INDEX emp_name_idx ON employees(last_name, first_name);Index created.
— 创建函数索引
CREATE INDEX emp_hire_date_idx ON employees(TRUNC(hire_date));Index created.
— 重建索引
ALTER INDEX emp_dept_id_idx REBUILD;Index altered.
— 收集统计信息
EXEC DBMS_STATS.GATHER_TABLE_STATS(‘HR’, ‘EMPLOYEES’);PL/SQL procedure successfully completed.
5. 内存调优
内存调优是提高数据库性能的重要因素，通过合理配置内存参数可以减少磁盘I/O，提高系统性能。
SELECT name, value, description
FROM v$parameter
WHERE name LIKE ‘%memory%’ OR name LIKE ‘%sga%’ OR name LIKE ‘%pga%’;NAME VALUE DESCRIPTION
———————————— ———- —————————————-
memory_target 1073741824 Memory Target Size (bytes)
memory_max_target 1073741824 Maximum Memory Target Size (bytes)
sga_target 671088640 SGA Target Size (bytes)
pga_aggregate_target 335544320 PGA Aggregate Target (bytes)
— 修改内存参数
ALTER SYSTEM SET memory_target = ‘2G’ SCOPE=SPFILE;ALTER SYSTEM SET sga_target = ‘1.2G’ SCOPE=SPFILE;ALTER SYSTEM SET pga_aggregate_target = ‘800M’ SCOPE=SPFILE;System altered.
System altered.
System altered.
— 重启数据库使参数生效
SHUTDOWN IMMEDIATE;STARTUP;– 查看SGA使用情况
SELECT * FROM v$sga;NAME VALUE
—————————— ———-
Fixed Size 2923504
Variable Size 402653184
Database Buffers 880803840
Redo Buffers 5455872
— 查看PGA使用情况
SELECT * FROM v$pga_target_advice;PGA_TARGET_FOR_ESTIMATE PGA_TARGET_FACTOR ESTD_PGA_CACHE_HIT_PERCENTAGE ESTD_OVERALLOC_COUNT
———————– —————– ——————————- ——————–
16777216 0.05 22 3
33554432 0.10 26 3
67108864 0.20 35 2
134217728 0.40 52 1
268435456 0.80 74 0
335544320 1.00 82 0
671088640 2.00 91 0
1342177280 4.00 95 0
6. 存储调优
存储调优是提高数据库性能的重要方面，通过合理配置存储可以减少I/O等待时间，提高系统性能。
SELECT tablespace_name, file_id, file_name, bytes/1024/1024 AS size_mb, maxbytes/1024/1024 AS max_size_mb
FROM dba_data_files;TABLESPACE_NAME FILE_ID FILE_NAME SIZE_MB MAX_SIZE_MB
—————————— ——- ——————————————— ———- ———-
SYSTEM 1 /u01/app/oracle/oradata/ORCL/system01.dbf 700 34359738368
SYSAUX 2 /u01/app/oracle/oradata/ORCL/sysaux01.dbf 550 34359738368
UNDOTBS1 3 /u01/app/oracle/oradata/ORCL/undotbs01.dbf 200 34359738368
USERS 4 /u01/app/oracle/oradata/ORCL/users01.dbf 50 34359738368
— 查看表空间使用率
SELECT tablespace_name, SUM(bytes)/1024/1024 AS used_mb, SUM(maxbytes)/1024/1024 AS max_mb,
(SUM(bytes)/SUM(maxbytes))*100 AS usage_percent
FROM dba_data_files
GROUP BY tablespace_name;TABLESPACE_NAME USED_MB MAX_MB USAGE_PERCENT
—————————— ———- ———- ————
SYSTEM 700 34359738368 0
SYSAUX 550 34359738368 0
UNDOTBS1 200 34359738368 0
USERS 50 34359738368 0
— 添加数据文件
ALTER TABLESPACE users ADD DATAFILE ‘/u01/app/oracle/oradata/ORCL/users02.dbf’ SIZE 100M AUTOEXTEND ON NEXT 10M MAXSIZE UNLIMITED;Tablespace altered.
— 移动表到新表空间
ALTER TABLE employees MOVE TABLESPACE users;Table altered.
— 重建索引
ALTER INDEX pk_employees REBUILD TABLESPACE users;Index altered.
7. 实例参数调优
实例参数调优是提高数据库性能的重要手段，通过合理配置实例参数可以优化数据库的运行环境。
SELECT name, value, description
FROM v$parameter
WHERE name IN (‘db_block_size’, ‘processes’, ‘sessions’, ‘open_cursors’, ‘pga_aggregate_target’, ‘sga_target’);NAME VALUE DESCRIPTION
———————————— ———- —————————————-
db_block_size 8192 size of database blocks
processes 300 maximum number of operating system user processes
that can connect to the database
sessions 472 maximum number of sessions
open_cursors 300 maximum number of open cursors per session
pga_aggregate_target 335544320 PGA Aggregate Target (bytes)
sga_target 671088640 SGA Target Size (bytes)
— 修改实例参数
ALTER SYSTEM SET processes = 400 SCOPE=SPFILE;ALTER SYSTEM SET sessions = 555 SCOPE=SPFILE;ALTER SYSTEM SET open_cursors = 500 SCOPE=SPFILE;System altered.
System altered.
System altered.
— 重启数据库使参数生效
SHUTDOWN IMMEDIATE;STARTUP;– 查看共享池使用情况
SELECT * FROM v$sgastat WHERE name LIKE ‘%free%’ OR name LIKE ‘%library cache%’;POOL NAME BYTES
———— —————————— ———-
shared pool free memory 10485760
shared pool library cache 52428800
— 清除共享池
ALTER SYSTEM FLUSH SHARED_POOL;System altered.
— 清除缓冲区缓存
ALTER SYSTEM FLUSH BUFFER_CACHE;System altered.
8. 最佳实践
1. 定期监控数据库性能，及时发现性能瓶颈
2. 优化SQL语句，使用绑定变量，避免硬解析
3. 合理创建和使用索引，提高查询性能
4. 定期收集统计信息，确保优化器选择正确的执行计划
5. 合理配置内存参数，平衡SGA和PGA的使用
6. 优化存储配置，减少I/O等待时间
7. 合理配置实例参数，优化数据库运行环境
8. 定期备份数据库，确保数据安全
9. 定期更新Oracle数据库补丁，修复性能问题
10. 制定性能调优策略，持续优化数据库性能
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