提高ORACLE数据库的查询统计速度


大型数据库系统中往往要用到查询统计,但是对于数据量大的系统,用户在进行复杂的查询统计时往往感到速度很慢,不能满足应用要求,这就要求我们在设计数据库系统时进行合理设置,提高查询统计的速度。本文结合笔者的项目开发经验,阐述具体的设置方法。

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500M,用于存放本系统的数据;

2)段盘区的初始大小为10K,增长大小为10K,增长幅度为1;

3)用户临时空间增大40M;

4)系统临时表空间和回滚段表空间增大40M,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 < 512000 AND

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

  1<desktop netware=""> $ init.ora Copyr (c) 1991 Oracle   
  2  
  3#   
  4  
  5##############################################################################   
  6  
  7# Example INIT.ORA file   
  8  
  9#   
 10  
 11# This file is provided by Oracle Corporation to help you customize   
 12  
 13# your RDBMS installation for your site. Important system parameters   
 14  
 15# are discussed, and example settings given.   
 16  
 17#   
 18  
 19# Some parameter settings are generic to any size installation.   
 20  
 21# For parameters that require different values in different size   
 22  
 23# installations, three scenarios have been provided: SMALL, MEDIUM   
 24  
 25# and LARGE. Any parameter that needs to be tuned according to   
 26  
 27# installation size will have three settings, each one commented   
 28  
 29# according to installation size.   
 30  
 31#   
 32  
 33# Use the following table to approximate the SGA size needed for the   
 34  
 35# three scenarious provided in this file:   
 36  
 37#   
 38  
 39# -------Installation/Database Size------   
 40  
 41# SMALL MEDIUM LARGE   
 42  
 43# Block 2K 4500K 6800K 17000K   
 44  
 45# Size 4K 5500K 8800K 21000K   
 46  
 47#   
 48  
 49# To set up a database that multiple instances will be using, place   
 50  
 51# all instance-specific parameters in one file, and then have all   
 52  
 53# of these files point to a master file using the IFILE command.   
 54  
 55# This way, when you change a public   
 56  
 57# parameter, it will automatically change on all instances. This is   
 58  
 59# necessary, since all instances must run with the same value for many   
 60  
 61# parameters. For example, if you choose to use private rollback segments,   
 62  
 63# these must be specified in different files, but since all gc_*   
 64  
 65# parameters must be the same on all instances, they should be in one file.   
 66  
 67#   
 68  
 69# INSTRUCTIONS: Edit this file and the other INIT files it calls for   
 70  
 71# your site, either by using the values provided here or by providing   
 72  
 73# your own. Then place an IFILE= line into each instance-specific   
 74  
 75# INIT file that points at this file. ###############################################################################   
 76  
 77db_name = oracle   
 78  
 79db_files = 20   
 80  
 81control_files = C:\ORAWIN95\DATABASE\ctl1orcl.ora 
 82
 83compatible = 7.3.0.0.0 
 84
 85db_file_multiblock_read_count = 8 # INITIAL   
 86  
 87# db_file_multiblock_read_count = 8 # SMALL   
 88  
 89# db_file_multiblock_read_count = 16 # MEDIUM   
 90  
 91# db_file_multiblock_read_count = 32 # LARGE   
 92  
 93db_block_buffers = 200 # INITIAL   
 94  
 95# db_block_buffers = 200# SMALL   
 96  
 97# db_block_buffers = 550 # MEDIUM   
 98  
 99# db_block_buffers = 3200 # LARGE   
100  
101shared_pool_size = 3500000 # INITIAL   
102  
103# shared_pool_size = 3500000 # SMALL   
104  
105# shared_pool_size = 6000000 # MEDIUM   
106  
107# shared_pool_size = 9000000 # LARGE   
108  
109log_checkpoint_interval = 10000 
110
111processes = 50 # INITIAL   
112  
113# processes = 50 # SMALL   
114  
115# processes = 100 # MEDIUM   
116  
117# processes = 200 # LARGE   
118  
119dml_locks = 100 # INITIAL   
120  
121# dml_locks = 100 # SMALL   
122  
123# dml_locks = 200 # MEDIUM   
124  
125# dml_locks = 500 # LARGE 
126
127log_buffer = 8192 # INITIAL   
128  
129# log_buffer = 8192 # SMALL   
130  
131# log_buffer = 32768 # MEDIUM   
132  
133# log_buffer = 163840 # LARGE 
134
135sequence_cache_entries = 10 # INITIAL   
136  
137# sequence_cache_entries = 10 # SMALL   
138  
139# sequence_cache_entries = 30 # MEDIUM   
140  
141# sequence_cache_entries = 100# LARGE 
142
143sequence_cache_hash_buckets = 10 # INITIAL   
144  
145# sequence_cache_hash_buckets = 10 # SMALL   
146  
147# sequence_cache_hash_buckets = 23 # MEDIUM   
148  
149# sequence_cache_hash_buckets = 89 # LARGE   
150  
151# audit_trail = true # if you want auditing   
152  
153# timed_statistics = true # if you want timed statistics   
154  
155max_dump_file_size = 10240 # limit trace file size to 5 Meg each   
156  
157# log_archive_start = true # if you want automatic archiving   
158  
159log_archive_dest=%ORACLE_HOME%\DATABASE\ARCHIVE 
160
161# define directories to store trace and alert files   
162  
163background_dump_dest=%RDBMS73%\trace   
164  
165user_dump_dest=%RDBMS73%\trace 
166
167db_block_size = 2048 
168
169snapshot_refresh_processes = 1 
170
171remote_login_passwordfile = shared   
172  
173---  
174  
175  
176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。   
177  
178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。</desktop>
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