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learning v$ view-> v$sqltext&v$sqlarea

2011-09-28 08:49 316 查看

V$SQLTEXT

This view contains the complete SQL text for the SQL statements in the shared pool.

Note:

V$SQLAREA

only contains only the first 1000 characters.

Useful Columns for V$SQLTEXT

HASH_VALUE

: Hash value for the SQL statement

ADDRESS

: Address of the SQL statement cursor in SGA

SQL_TEXT

: Statement text in 64 character chunks

PIECE

: Ordering information for the SQL statement pieces

Join Columns for V$SQLTEXT

Table 24-27 lists the join columns for

V$SQLTEXT

.

[b]Table 24-27 Join Columns for V$SQLTEXT[/b]


Column	View	Joined Column(s)
HASH_VALUE, ADDRESS	V$SQL, V$SESSION	HASH_VALUE, ADDRESS
HASH_VALUE. ADDRESS	V$SESSION	SQL_HASH_VALUE. SQL_ADDRESS

Example 24-30 Finding the SQL Statement for a Hash Value

SELECT sql_text
FROM V$SQLTEXT
WHERE hash_value = 228801498
ORDER BY piece;

SQL_TEXT
----------------------------------------------------------------
select dbsu.primary_flag, i.site_use_code, i.rowid
from ra_customers dbc, ra_addresses dbad, ra_site_uses dbsu, ra_customers_
interface i
where (((((((i.orig_system_customer_ref=dbc.orig_system_reference and
dbad.address_id=dbsu.address_id) and i.site_use_code=dbsu.site_use_code) and
dbsu.status='A') and dbad.customer_id=dbc.customer_id) and i.request_id=:b0) and
nvl(i.validated_flag,'N')<>'Y') and ((i.primary_site_use_flag='Y' and
dbsu.primary_flag='Y') or dbsu.site_use_code in ('STMTS','DUN','LEGAL')))

V$SQLAREA

This view keeps track of all the shared cursors present in the shared pool. It has one row for every SQL statement present in the shared pool. It is an invaluable view for finding the resource usage of a SQL statement.

Information columns in V$SQLAREA

HASH_VALUE

: Hash value of the SQL statement

ADDRESS

: SGA address for the SQL statement
These two columns are used to identify the SQL statement. Sometimes, two different statements could hash to the same value. In such cases, it is necessary to use the address along with the hash_value.

PARSING_USER_ID

: User who parsed the first cursor for the statement

VERSION_COUNT

: Number of cursors for the statement

KEPT_VERSIONS

: Cursors of the statement pinned using

DBMS_SHARED_POOL

KEEP

()

SHARABLE_MEMORY

: Total shared memory used by the cursor

PERSISTENT_MEMORY

: Total persistent memory used by the cursor

RUNTIME_MEMORY

: Total runtime memory used by the cursor

SQL_TEXT

: Up to first 1000 characters of SQL statement

MODULE

ACTION

: Information about the session parsing the first cursor if set using

DBMS_APPLICATION_INFO

Other Useful Columns in V$SQLAREA

These columns get incremented with each execution of the statement.

BUFFER_GETS

: Number of logical reads for this statement

DISK_READS

: Number of physical reads for this statement

SORTS

: Number of sorts for this statement

CPU_TIME

: CPU time used for parsing and executing this statement

ELAPSED_TIME

: Elapsed time for parsing and executing this statement

PARSE_CALLS

: Number of parse calls (hard and soft) for this statement

EXECUTIONS

: Number of times this statement was executed

INVALIDATIONS

: Number of times the cursors for this statement have been invalidated

LOADS

: Number of loads (and reloads) for this statement

ROWS_PROCESSED

: Total number of rows this statement returns

Join Columns in V$SQLAREA

Table 24-26 lists the join columns for

V$SQLAREA

.[b]Table 24-26 Join Columns for V$SQLAREA[/b]


Column	View	Joined Column(s)
HASH_VALUE, ADDRESS	V$SESSION	SQL_HASH_VALUE, SQL_ADDRESS
HASH_VALUE, ADDRESS	V$SQLTEXT, V$SQL, V$OPEN_CURSOR	HASH_VALUE, ADDRESS
SQL_TEXT	V$DB_OBJECT_CACHE	NAME

Example 24-28 Finding Resource-intensive SQL

There are several costs you can use:Total logical I/O (LIO), LIO for each execution
Total physical I/O (PIO), PIO for each execution
PIO/LIO (poor cache hit ratio)
parse_calls, parse_calls for each executions

SELECT hash_value, executions, buffer_gets, disk_reads, parse_calls
FROM V$SQLAREA
WHERE buffer_gets > 10000000
OR disk_reads > 1000000
ORDER BY buffer_gets + 100*disk_reads DESC;

HASH_VALUE EXECUTIONS BUFFER_GETS DISK_READS PARSE_CALLS
---------- ---------- ----------- ---------- -----------
2676594883        126     7583140    6199113         126
4074144966        126     7264362    6195433          49
228801498        136   236116544    2371187         136
360282550       5467    21102603    4476317        2355
1559420740        201     8197831    4537591          39
3213702248   28039654   364516977         44         131
1547710012        865     7579025    3337735         865
3000880481       4481     3676546    2212658        2885
1398193708       4946    73018658    1515257        1418
1052917712    8342025   201246652      38240      327462
371697988          7    74380777     862611           7
1514306888    3922461    29073852    1223482         268
1848522009          1     1492281    1483635           1
1478599096   28042103   140210513        594         164
226079402      21473    22121577    1034787        4484
478652562       4468    21669366    1020370        4438
2054874295      73520   118272694      29987       73520

Note: If
a statement is executing for the first time on the system and responsible for large fraction of the current resource usage, then this statement does not find that statement, because the

BUFFER_GETS

and

DISK_READS

statistics do not
get updated until the statement finishes execution.

Example 24-29 Finding Resources Used by a SQL Statement

SELECT hash_value, buffer_gets, disk_reads, executions, parse_calls
FROM V$SQLAREA
WHERE hash_Value = 228801498
AND address = hextoraw('CBD8E4B0');

HASH_VALUE BUFFER_GETS DISK_READS EXECUTIONS PARSE_CALLS
---------- ----------- ---------- ---------- -----------
228801498   236116544    2371187        136         136

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标签： sql parsing buffer disk join statistics

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