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使用db2look 重新创建优化器访问计划
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编辑：华夏媒体 作者：未知 来源：网络 时间：2006-07-29 总浏览量：4724 |
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-- Environment Variables settings
---------------------------------
!db2set DB2_INLIST_TO_NLJN=yes;
!db2set DB2_HASH_JOIN=yes;
除了以上设置，还应在数据库配置中注意下列配置：
db2 get db cfg for sample > dbcfg_sample.out
Database heap (4KB) (DBHEAP) = 600
SQL statement heap (4KB) (STMTHEAP) = 2048
Number of frequent values retained (NUM_FREQVALUES) = 10
Number of quantiles retained (NUM_QUANTILES) = 20
确保在修改数据库管理器配置（dbm cfg）之后停止并启动该实例。对于 sample 数据库，按下列方式对 ORG 和 SALES 表运行 runstats：
db2 connect to sample
db2 runstats on table <schema>.org with distribution and indexes all
db2 runstats on table <schema>.sales with distribution and indexes all
db2 terminate
现在，通过执行 EXPLAIN.DDL 文件生成 EXPLAIN 表，该文件在 <install directory>\sqllib\misc 目录下：
db2 connect to sample
db2 -tvf <intall path>\EXPLAIN.DDL
db2 terminate
在名为 query.sql 的文件中保存下列命令：
connect to sample
set current explain mode explain
select * from org a, staff b where a.deptnumb=b.dept and b.dept=15
set current explain mode no
terminate
现在，按下列方式执行该文件：
db2 -tvf query.sql
上面将仅仅以解释模式编译查询。您将在屏幕上看到：
C:\>db2 -tvf query.sql
connect to sample
Database Connection Information
Database server = DB2/NT 8.2.1
SQL authorization ID = SKAPOOR
Local database alias = SAMPLE
set current explain mode explain
DB20000I The SQL command completed successfully.
select * from org a, staff b where a.deptnumb=b.dept and b.dept=15
SQL0217W The statement was not executed as only Explain information requests
are being processed. SQLSTATE=01604
set current explain mode no
DB20000I The SQL command completed successfully.
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