What is plan hash?
A query plan hash is a hash made from the operations in a specific execution plan. I’d like to say that every single execution plan has a different hash, but there might be one or two hash collisions out there.
What is Plan_hash_value?
PLAN_HASH_VALUE – How equal (and stable?) are your execution plans – part 1. “Numerical representation of the SQL plan for the cursor. Comparing one PLAN_HASH_VALUE to another easily identifies whether or not two plans are the same (rather than comparing the two plans line by line).”
What is SQL ID and Plan_hash_value in Oracle?
A single SQL statement ( sql_id / hash_value ) can have multiple different plans ( plan_hash_value ) and multiple different SQL statements can share the same plan. So, for example, if I write two different SQL statements that are querying a particular row from the EMP table, I’ll get the same plan_hash_value .
What is Explain plan in Oracle?
The EXPLAIN PLAN statement displays execution plans chosen by the Oracle optimizer for SELECT , UPDATE , INSERT , and DELETE statements. A statement’s execution plan is the sequence of operations Oracle performs to run the statement.
What is the difference between hash value and Plan hash value in Oracle?
Hash_value of a SQL statement is generated from the text of an SQL statement and plan_hash_value is generated from the execution plan of that SQL statement[ More accurately, from that child cursors’ execution plan and exactly what is involved in generating plan_hash_value is not published].
Why does plan hash value changes in Oracle?
Let’s explore why the plans change. (1) STATS Changed : The plan may change because you changed the data in your database. The new statistics cause Oracle to change its mind and you get a new plan. (2) STATS Did Not Change : The plan may change because you changed the data in you database.
Where can I find SQLID from Plan hash value?
SELECT SQL_ID,SQL_TEXT FROM V$SQLAREA WHERE PLAN_HASH_VALUE=’1578910895′ AND SQL_TEXT LIKE ‘%SELECT * FROM HR. EMP%’;
What is Coe_xfr_sql_profile SQL in Oracle?
The coe_xfr_sql_profile. sql script generates another script that, in turn, contains the commands to create a manual custom SQL Profile out of a known plan that resides in RAM (library cache) or from the AWR dba_hist_sqlplan table.
What is SQL profile in Oracle?
A SQL profile is a set of auxiliary information specific to a SQL statement. Conceptually, a SQL profile is to a SQL statement what statistics are to a table or index. This information can improve optimizer cardinality and selectivity estimates, which in turn leads the optimizer to select better plans.
