| 标题 | 提高Oracle的查询统计速度方法简介 |
| 内容 | 以Oracle7.33数据库系统为例，我们在开发大型Oracle数据库系统时结合项目的特点，本着安全、高效的原则对数据库进行了一些物理设计，从而大大提高了数据库的查询统计速度。总结为如下几点： 1）扩大数据表空间到500MB，用于存放本系统的数据； 2）段盘区的初始大小为10KB，增长大小为10KB，增长幅度为1； 3）用户临时空间增大40MB； 4）系统临时表空间和回滚段表空间增大40MB，并且新建4个回滚段； 5）需要经常联结查询，而且数据量又大的库存表、名录表、收发料表放在一簇内； 6）提供定时备份，备份文件放在另外的机器上。 设置数据表空间的SQL语句如下： CREATE TABLESPACE WXGL_DATA1 DATAFILE 'WXGL_DATA1.ORA' SIZE 500M ONLINE; 增加系统临时表空间和回滚段表空间的SQL语句如下： ALTER TABLESPACE TEMPORARY_DATA ADD DATAFILE 'TMP2ORCL.ORA' SIZE 40M; ALTER TABLESPACE ROLLBACK_DATA ADD DATAFILE 'RBS2ORCL.ORA' SIZE 40M; 将数据空间设置在指定的数据文件的SQL语句如下： CREATE USER ZBGL IDENTIFIED BY ZBGL; GRANT DBA TO ZBGL; ALTER USER ZBGL DEFAULT TABLESPACE WXGL_DATA1 TEMPORARY TABLESPACE TEMPORARY_DATA; 设置五个回滚段的SQL语句如下： SELECT SEGMENT_NAME FROM DBA_ROLLBACK_SEGS WHERE INITIAL_EXTENT UPPPER(OWNER) = 'PUBLIC'; SELECT UPPER(STATUS) FROM DBA_ROLLBACK_SEGS WHERE UPPER(SEGMENT_NAME) = '' ALTER ROLLBACK SEGMENT RB1 OFFLINE; ALTER ROLLBACK SEGMENT RB2 OFFLINE; ALTER ROLLBACK SEGMENT RB3 OFFLINE; ALTER ROLLBACK SEGMENT RB4 OFFLINE; ALTER ROLLBACK SEGMENT RB5 OFFLINE; DROP ROLLBACK SEGMENT RB1; DROP ROLLBACK SEGMENT RB2; DROP ROLLBACK SEGMENT RB3; DROP ROLLBACK SEGMENT RB4; DROP ROLLBACK SEGMENT RB5; CREATE PUBLIC ROLLBACK SEGMENT RB1 TABLESPACE ROLLBACK_DATA STORAGE (INITIAL 512000 NEXT 512000 MAXEXTENTS 121); CREATE PUBLIC ROLLBACK SEGMENT RB2 TABLESPACE ROLLBACK_DATA STORAGE (INITIAL 512000 NEXT 512000 MAXEXTENTS 121); CREATE PUBLIC ROLLBACK SEGMENT RB3 TABLESPACE ROLLBACK_DATA STORAGE (INITIAL 512000 NEXT 512000 MAXEXTENTS 121); CREATE PUBLIC ROLLBACK SEGMENT RB4 TABLESPACE ROLLBACK_DATA STORAGE (INITIAL 512000 NEXT 512000 MAXEXTENTS 121); CREATE PUBLIC ROLLBACK SEGMENT RB5 TABLESPACE ROLLBACK_DATA STORAGE (INITIAL 512000 NEXT 512000 MAXEXTENTS 121); ALTER ROLLBACK SEGMENT RB1 ONLINE; ALTER ROLLBACK SEGMENT RB2 ONLINE; ALTER ROLLBACK SEGMENT RB3 ONLINE; ALTER ROLLBACK SEGMENT RB4 ONLINE; ALTER ROLLBACK SEGMENT RB5 ONLINE; COMMIT; 将数据量大的库存表等放在一簇内的SQL语句如下： KCB='CREATE TABLE QC_KCB( ' +' CKNM NUMBER(8) ,' +' QCNM NUMBER(10) ,' +' CKKC NUMBER(12,2),' +' SNCKKC NUMBER(12,2),' +' LDJ NUMBER(12,2),' +' BZ VARCHAR(100),' +' PRIMARY KEY(CKNM,QCNM))' +' TABLESPACE WXGL_DATA1 ' ; （大数据量的库存表等放在WXGL_DATA1) QCFL = 'CREATE TABLE QC_QCFL ' + '(FLBH NUMBER(2) PRIMARY KEY,' + ' FLMC VARCHAR(20) ' + ' ) ' +' TABLESPACE WXGL_DATA2 ' ;(其他表放在WXGL_DATA2） 系统的基础数据库存表、名录表大约有数据80M；一个单位一般每年收发300次，收发料单大约有数据50M；系统冗余数据100M，系统辅助数据10M；因此，系统总共需要空间大约是240M，现在系统开辟数据空间500M，完全满足存储要求。由于系统使用了冗余数据，在查询常用数据时，避免了多表联结查询的情况，这样，虽然使用了更多的存储空间，但查询效率大幅度提高；同时，系统将需要经常联结查询的数据放在一簇，即将存放这些数据的空间在物理上相邻，这样也使查询速度大大提高。 另外在oracle7.33数据库的Database目录下有一个Initorcl.ora文件，改变其中的设置也可以提高查询统计速度。该文件的内容如下： # # $Header: init.ora 1.2 94/10/18 16:12:36 gdudey Osd $ init.ora Copyr (c) 1991 Oracle # ########################################################## # Example INIT.ORA file # # This file is provided by Oracle Corporation to help you customize # your RDBMS installation for your site. Important system parameters # are discussed, and example settings given. # # Some parameter settings are generic to any size installation. # For parameters that require different values in different size # installations, three scenarios have been provided: SMALL, MEDIUM # and LARGE. Any parameter that needs to be tuned according to # installation size will have three settings, each one commented # according to installation size. # # Use the following table to approximate the SGA size needed for the # three scenarious provided in this file: # # -------Installation/Database Size------ # SMALL MEDIUM LARGE # Block 2K 4500K 6800K 17000K # Size 4K 5500K 8800K 21000K # # To set up a database that multiple instances will be using, place # all instance-specific parameters in one file, and then have all # of these files point to a master file using the IFILE command. # This way, when you change a public # parameter, it will automatically change on all instances. This is # necessary, since all instances must run with the same value for many # parameters. For example, if you choose to use private rollback segments, # these must be specified in different files, but since all gc_* # parameters must be the same on all instances, they should be in one file. # # INSTRUCTIONS: Edit this file and the other INIT files it calls for # your site, either by using the values provided here or by providing # your own. Then place an IFILE= line into each instance-specific # INIT file that points at this file. ################################################################# db_name = oracle db_files = 20 control_files = C:\ORAWIN95\DATABASE\ctl1orcl.ora compatible = 7.3.0.0.0 db_file_multiblock_read_count = 8 # INITIAL # db_file_multiblock_read_count = 8 # SMALL # db_file_multiblock_read_count = 16 # MEDIUM # db_file_multiblock_read_count = 32 # LARGE db_block_buffers = 200 # INITIAL # db_block_buffers = 200# SMALL # db_block_buffers = 550 # MEDIUM # db_block_buffers = 3200 # LARGE shared_pool_size = 3500000 # INITIAL # shared_pool_size = 3500000 # SMALL # shared_pool_size = 6000000 # MEDIUM # shared_pool_size = 9000000 # LARGE log_checkpoint_interval = 10000 processes = 50 # INITIAL # processes = 50 # SMALL # processes = 100 # MEDIUM # processes = 200 # LARGE dml_locks = 100 # INITIAL # dml_locks = 100 # SMALL # dml_locks = 200 # MEDIUM # dml_locks = 500 # LARGE log_buffer = 8192 # INITIAL # log_buffer = 8192 # SMALL # log_buffer = 32768 # MEDIUM # log_buffer = 163840 # LARGE sequence_cache_entries = 10 # INITIAL # sequence_cache_entries = 10 # SMALL # sequence_cache_entries = 30 # MEDIUM # sequence_cache_entries = 100# LARGE sequence_cache_hash_buckets = 10 # INITIAL # sequence_cache_hash_buckets = 10 # SMALL # sequence_cache_hash_buckets = 23 # MEDIUM # sequence_cache_hash_buckets = 89 # LARGE # audit_trail = true # if you want auditing # timed_statistics = true # if you want timed statistics max_dump_file_size = 10240 # limit trace file size to 5 Meg each # log_archive_start = true # if you want automatic archiving log_archive_dest=%ORACLE_HOME%\DATABASE\ARCHIVE # define directories to store trace and alert files background_dump_dest=%RDBMS73%\trace user_dump_dest=%RDBMS73%\trace db_block_size = 2048 snapshot_refresh_processes = 1 remote_login_passwordfile = shared 可以修改该文件的db_file_multiblock_read_count，db_block_buffers，shared_pool_size，processes ，log_buffer，sequence_cache_entries，sequence_cache_hash_buckets等项（文件中均有提示），根据需要和系统使用的数据库服务器的特点适当改大数值，可以提高查询统计速度。这里要注意的是，必须将 log_archive_start = true 项改为False，设置才能生效。 本文介绍的Oracle数据库设置方法均在用户实际使用中经过了严格测试，证明是有效和实用的。 |
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