(转)explain、db2exfmt 命令的使用：文本输出执行计划

原文：http://blog.51cto.com/freebile/1068610

　

db2有图形执行计划显示工具,如果没有图形环境,如unix主机,可以生成文本的
文件来显示执行计划
1.如果第一次执行,请先 connect to dbname,
执行db2 -tvf $HOME/sqllib/misc/EXPLAIN.DDL建立执行计划表
2.db2 set current explain mode explain
设置成解释模式,并不真正执行下面将发出的sql命令

3.db2 "select count(*) from DOA.ODS_SFC_SALE_BARCODE_T"  
执行你想要分析的sql语句

4.db2 set current explain mode no
取消解释模式
5.db2exfmt -d sample  -g TIC -w -l -s % -n % -o db2exmt.out
执行计划输出到文件db2exmt.out

相关参数设置可以参考
(This application formats the contents of the Explain tables.
Given a database name and other qualifying information, this tool will,
query the Explain tables for information and format the results.

Syntax is:

db2exfmt [[-1] [-d <dbname>;] [-e <schema>;] [-f O] [-h] [-l] [-n <name>;] [-o <outfile>;]
          [-s <schema>;] [-t]] [-u <user>; <pw>;] [-w <timestamp>;] [-# <sectnbr>;] [-v <srcvers>;]

Input Fields:
        -d <dbname>;     = database name containing packages
        -e <schema>;     = Explain table schema
        -f O            = Formatting flags (O = Operator summary)
        -g[x]  [O[T|F]IC] - Graph plan. x - turn off options (default is to turn them on) Options include:
                             O = only generate graph
                             T = Include Total Cost in graph
                             F = Include First Tuple Cost in graph
                             I = Include I/O Cost in graph
                             C = Include Cardinality in graph
                          Any combination of these options is allowed,
                          except 'F' and 'T', which are mutually exclusive.
        -h              = help
        -l              = respect package name case
        -n <name>;       = name of source of Explain
                          request (SOURCE_NAME)
        -no_map_char    = do no map a non-printable character to a '.'
        -no_prompt      = do not prompt for user input
        -o <outfile>;    = name of output file
        -r <requester>;  = id of explain requester
        -s <schema>;     = Schema or qualifier of source of Explain
                          request (SOURCE_SCHEMA)
        -t              = terminal output desired
        -u <user>; <pw>;  = user ID and password for connecting to database
        -v <srcvers>;    = Source Version of source of Explain request (default %)
        -w <timestamp>;  = Explain timestamp (use -1 to get newest Explain request)
        -# <sectnbr>;    = section number in source (use zero for all sections)

-1              = Use defaults -e % -n % -s % -v % -w -1 -# 0   If Explain schema is not supplied, the contents of the environment
        variable $USER, or $USERNAME will be used as a default. If this
        variable is not found, the user will be prompted for an Explain schema.

Source name, source schema, and Explain timestamp may be supplied
        in LIKE predicate form, which allows percent sign (%) and
        underscore (_) to be used as pattern matching characters to select
        multiple sources with one invocation.

Prompting will occur for all fields that are not supplied or are
        incompletely specified (except for the -h, -l and -no_map_char options).

If -o is specified without a file name, and -t is not specified,
        the user will be prompted for a file name (the default name is
        db2exfmt.out).

If neither -o nor -t is specified, the user will be prompted for
        a file name (the default is terminal output).

If -o and -t are both specified, then the output will be directed
        to the terminal.
)

6.查看输出文件分析sql的运行开销,示例输出如下

-------------------

DB2 Universal Database Version 9.5, 5622-044 (c) Copyright IBM Corp. 1991, 2007
Licensed Material - Program Property of IBM
IBM DATABASE 2 Explain Table Format Tool

******************** EXPLAIN INSTANCE ********************

DB2_VERSION:   09.05.4
SOURCE_NAME:   SQLC2G15
SOURCE_SCHEMA:   NULLID  
SOURCE_VERSION:  
EXPLAIN_TIME:   2012-11-23-16.02.53.924371 
EXPLAIN_REQUESTER:  DOAADMIN

Database Context:
----------------
 Parallelism:   None
 CPU Speed:   4.959615e-07
 Comm Speed:   100
 Buffer Pool size:  438463
 Sort Heap size:  256
 Database Heap size:  2645
 Lock List size:  100
 Maximum Lock List:  20
 Average Applications:  1
 Locks Available:  1280

Package Context:
---------------
 SQL Type:   Dynamic
 Optimization Level:  5
 Blocking:   Block All Cursors
 Isolation Level:  Cursor Stability

---------------- STATEMENT 1  SECTION 201 ----------------
 QUERYNO:   3
 QUERYTAG:   CLP                 
 Statement Type:  Select
 Updatable:   No
 Deletable:   No
 Query Degree:   1

Original Statement:
------------------
select count(*) 
from DOA.ODS_SFC_SALE_BARCODE_T

Optimized Statement:
-------------------
SELECT Q3.$C0 
FROM 
   (SELECT COUNT(*) 
   FROM 
      (SELECT $RID$ 
      FROM DOA.ODS_SFC_SALE_BARCODE_T AS Q1) AS Q2) AS Q3

Access Plan:
-----------
 Total Cost:   51435.9
 Query Degree:  1

Rows 
     RETURN
     (   1)
      Cost 
       I/O 
       |
        1 
     GRPBY 
     (   2)
     51435.9 
      2027 
       |
     765027 
     IXSCAN
     (   3)
     51341.1 
      2027 
       |
     765027 
 INDEX: DOA     
    S_SALE_T1
       Q1

Extended Diagnostic Information:
--------------------------------

No extended Diagnostic Information for this statement.

Plan Details:
-------------

1) RETURN: (Return Result)
  Cumulative Total Cost:   51435.9
  Cumulative CPU Cost:   1.53426e+09
  Cumulative I/O Cost:   2027
  Cumulative Re-Total Cost:  747.847
  Cumulative Re-CPU Cost:  1.50787e+09
  Cumulative Re-I/O Cost:  0
  Cumulative First Row Cost:  51435.9
  Estimated Bufferpool Buffers:  2028

Arguments:
  ---------
  BLDLEVEL: (Build level)
   DB2 v9.5.0.4 : s090429
  HEAPUSE : (Maximum Statement Heap Usage)
   80 Pages
  PREPTIME: (Statement prepare time)
            1 milliseconds
  STMTHEAP: (Statement heap size)
   6402

Input Streams:
  -------------
   3) From Operator #2

Estimated number of rows:  1
    Number of columns:   1
    Subquery predicate ID:   Not Applicable

Column Names:
    ------------
    +Q4.$C0

2) GRPBY : (Group By)
  Cumulative Total Cost:   51435.9
  Cumulative CPU Cost:   1.53426e+09
  Cumulative I/O Cost:   2027
  Cumulative Re-Total Cost:  747.847
  Cumulative Re-CPU Cost:  1.50787e+09
  Cumulative Re-I/O Cost:  0
  Cumulative First Row Cost:  51435.9
  Estimated Bufferpool Buffers:  2028

Arguments:
  ---------
  AGGMODE : (Aggregration Mode)
   COMPLETE
  GROUPBYC: (Group By columns)
   FALSE
  GROUPBYN: (Number of Group By columns)
   0
  ONEFETCH: (One Fetch flag)
   FALSE

Input Streams:
  -------------
   2) From Operator #3

Estimated number of rows:  765027
    Number of columns:   0
    Subquery predicate ID:   Not Applicable

Output Streams:
  --------------
   3) To Operator #1

Estimated number of rows:  1
    Number of columns:   1
    Subquery predicate ID:   Not Applicable

Column Names:
    ------------
    +Q4.$C0

3) IXSCAN: (Index Scan)
  Cumulative Total Cost:   51341.1
  Cumulative CPU Cost:   1.343e+09
  Cumulative I/O Cost:   2027
  Cumulative Re-Total Cost:  652.991
  Cumulative Re-CPU Cost:  1.31662e+09
  Cumulative Re-I/O Cost:  0
  Cumulative First Row Cost:  50.0327
  Estimated Bufferpool Buffers:  2028

Arguments:
  ---------
  MAXPAGES: (Maximum pages for prefetch)
   2026
  PREFETCH: (Type of Prefetch)
   NONE
  ROWLOCK : (Row Lock intent)
   NEXT KEY SHARE
  SCANDIR : (Scan Direction)
   FORWARD
  TABLOCK : (Table Lock intent)
   INTENT SHARE
  TBISOLVL: (Table access Isolation Level)
   CURSOR STABILITY

Input Streams:
  -------------
   1) From Object DOA.S_SALE_T1

Estimated number of rows:  765027
    Number of columns:   1
    Subquery predicate ID:   Not Applicable

Column Names:
    ------------
    +Q1.$RID$

Output Streams:
  --------------
   2) To Operator #2

Estimated number of rows:  765027
    Number of columns:   0
    Subquery predicate ID:   Not Applicable

Objects Used in Access Plan:
---------------------------

Schema: DOA     
 Name:  ODS_SFC_SALE_BARCODE_T
 Type:  Table (reference only)

Schema: DOA     
 Name:  S_SALE_T1
 Type:  Index
   Time of creation:   2011-01-15-14.03.41.217506
   Last statistics update:  2012-04-23-18.45.51.142593
   Number of columns:   1
   Number of rows:   765027
   Width of rows:    -1
   Number of buffer pool pages:  50996
   Distinct row values:   No
   Tablespace name:   TS_INDEX_4K
   Tablespace overhead:   24.100000
   Tablespace transfer rate:  0.900000
   Source for statistics:   Single Node
   Prefetch page count:   128
   Container extent page count:  32
   Index clustering statistic:  97.000000
   Index leaf pages:   2026
   Index tree levels:   3
   Index full key cardinality:  18700
   Index first key cardinality:  18700
   Index first 2 keys cardinality: -1
   Index first 3 keys cardinality: -1
   Index first 4 keys cardinality: -1
   Index sequential pages:  0
   Index page density:   0
   Index avg sequential pages:  0
   Index avg gap between sequences:0
   Index avg random pages:  2026
   Fetch avg sequential pages:  -1
   Fetch avg gap between sequences:-1
   Fetch avg random pages:  -1
   Index RID count:   765027
   Index deleted RID count:  0
   Index empty leaf pages:  0
   Base Table Schema:   DOA     
   Base Table Name:   ODS_SFC_SALE_BARCODE_T
   Columns in index:
    BILL(A)

Base Table For Index Not Already Shown:
---------------------------------------

Schema: DOA     
 Name:  ODS_SFC_SALE_BARCODE_T
   Time of creation:   2011-01-15-13.40.52.458517
   Last statistics update:  2012-04-23-18.45.51.142593
   Number of data partitions:  1
   Number of columns:   21
   Number of rows:   765027
   Number of pages:   50996
   Number of pages with rows:  50996
   Table overflow record count:  0
   Indexspace name:   TS_INDEX_4K
   Tablespace name:   TS_4K
   Tablespace overhead:   24.100000
   Tablespace transfer rate:  0.900000
   Prefetch page count:   -1
   Container extent page count:  32

Long tablespace name:   TS_4K