What is an EXPLAIN in DB2.
How and what is the steps followed in EXPLAIN command. Can
all the queries be used in EXPLAIN command to check the
performance.
- 3 Answers
- 16768 Views
- IBM, I also Faced
- E-Mail Answers
Answers were Sorted based on User's Feedback
Answer / yuvaevergreen
>>Explain can be used to improve the performance of queries.
>>Explain command populates three tables
PLAN_TABLE,DSN_STATEMNT_TABLE,DSN_FUNCTION_TABLE. These
tables contains various info about the queries which can be
used for improving the performance.
>>Step1:PLAN_TABLE must be created.
>>Step2:Use explain sql or explain option in Bind to
populate the tables.
>>For example,explain plan set queryno=01 for select empname
from employee;
This would populate plan and statement table.Assigned
queryno would be 01.
>>Alternately EXPLAIN(YES) in BIND option.
>>Only select,insert,update,select for update,delete, delete
current of cursor,update current of cursor can be used in
explain.
| Is This Answer Correct ? | 7 Yes | 0 No |
Answer / s.v.venkata sivaprasad
explain is the db2 tool which used to improve db2
performance and provides best access path to package
| Is This Answer Correct ? | 1 Yes | 0 No |
Answer / ryan
Whenever we run a query,DB2 creates an access plan that specifies how it will access the requested data. This is created whenever the sql is compiled at bind time for static sql and before execution for dynamic sql.
DB2 bases the access paths on the SQL statements and also on the statistics and configuration parameters of the system.
Even when an sql is made efficient, it can become inefficient as data grows. So, we need to run DB2 runstats so as to keep updated statistics . DB2 config and storage can change and plans can be rebound. Db2 explain gives us the info for the plan, package, or SQL statement when it is bound. The output of the EXPLAIN is stored in user-created table called plan table. Whenever we want to tune a query, we need to go and check the plan table so as to get an idea of the access path DB2 optimizer is using.
http://mframes.blogspot.in/2015/01/db2-explain-and-plan-table-column-names.html
| Is This Answer Correct ? | 0 Yes | 0 No |
Can you define an Index if the table size less than 10 PAGES?
How do I import data from excel to db2?
How do you select a row using indexes in db2?
what is a plan and how do you refer the plan in the program?
What is innodb buffer pool?
What is the use of runstats in db2?
What does the REORG Utility do?
How is deadlock resolved?
how will i display the duplicate record's from a table... i don't want to eliminate ...i want to display the duplicate record...for example in my table i have 10 record's like record no(1,2,3,4,2,9,6,1) in this ...so i want to receive duplicates...
What is the maximum size of varchar data type in db2?
What is an inner join, and an outer join ?
What is db2 command?
COBOL 
