提高Oracle的查詢統計速度方法簡介
2024-08-29 13:33:48
供稿：網友
以Oracle7.33數據庫系統為例，我們在開發大型Oracle數據庫系統時結合項目的特點，本著安全、高效的原則對數據庫進行了一些物理設計，從而大大提高了數據庫的查詢統計速度?？偨Y為如下幾點： 1）擴大數據表空間到500MB，用于存放本系統的數據；
2）段盤區的初始大小為10KB，增長大小為10KB，增長幅度為1；
3）用戶臨時空間增大40MB；
4）系統臨時表空間和回滾段表空間增大40MB，并且新建4個回滾段；
5）需要經常聯結查詢，而且數據量又大的庫存表、名錄表、收發料表放在一簇內；
6）提供定時備份，備份文件放在另外的機器上。 設置數據表空間的SQL語句如下： CREATE TABLESPACE WXGL_DATA1 DATAFILE 'WXGL_DATA1.ORA' SIZE 500M ONLINE;增加系統臨時表空間和回滾段表空間的SQL語句如下： ALTER TABLESPACE TEMPORARY_DATA ADD DATAFILE 'TMP2ORCL.ORA' SIZE 40M;
ALTER TABLESPACE ROLLBACK_DATA ADD DATAFILE 'RBS2ORCL.ORA' SIZE 40M;將數據空間設置在指定的數據文件的SQL語句如下： CREATE USER ZBGL IDENTIFIED BY ZBGL;
GRANT DBA TO ZBGL;
ALTER USER ZBGL DEFAULT TABLESPACE WXGL_DATA1 TEMPORARY TABLESPACE TEMPORARY_DATA;設置五個回滾段的SQL語句如下： 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; 將數據量大的庫存表等放在一簇內的SQL語句如下：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 ' ; （大數據量的庫存表等放在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）系統的基礎數據庫存表、名錄表大約有數據80M；一個單位一般每年收發300次，收發料單大約有數據50M；系統冗余數據100M，系統輔助數據10M；因此，系統總共需要空間大約是240M，現在系統開辟數據空間500M，完全滿足存儲要求。由于系統使用了冗余數據，在查詢常用數據時，避免了多表聯結查詢的情況，這樣，雖然使用了更多的存儲空間，但查詢效率大幅度提高；同時，系統將需要經常聯結查詢的數據放在一簇，即將存放這些數據的空間在物理上相鄰，這樣也使查詢速度大大提高。 另外在oracle7.33數據庫的Database目錄下有一個Initorcl.ora文件，改變其中的設置也可以提高查詢統計速度。該文件的內容如下：#
# $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 可以修改該文件的db_file_multiblock_read_count，db_block_buffers，shared_pool_size，processes ，log_buffer，sequence_cache_entries，sequence_cache_hash_buckets等項（文件中均有提示），根據需要和系統使用的數據庫服務器的特點適當改大數值，可以提高查詢統計速度。這里要注重的是，必須將 log_archive_start = true 項改為False，設置才能生效。 本文介紹的Oracle數據庫設置方法均在用戶實際使用中經過了嚴格測試，證實是有效和實用的。
