Performance Tuning :: Select Query Taking Time Even After Using Parallel Hint?
Sep 25, 2013
select
serialnumber from product where productid in
(select /*+ full parallel(producttask 16) */productid from producttask where
startedtimestamp > to_date('2013-07-04 00:00:00', 'YYYY-MM-DD HH24:MI:SS')
and startedtimestamp < to_date('2013-07-05 00:00:00', 'YYYY-MM-DD HH24:MI:SS')
and producttasktypeid in
Does parallel hint works in cursor queries? The cursor query is something like :
cursor c is select /*+ parallel(s,8) */ from table ref_tab s ---- >> <where condition>;
The table ref_tab hold data for a single day at any point of time and gets truncate before loading the next days data.On average the table holds around 7 million rows and doesn't contains any index (think that's fine as all together we are loading the whole set).And, we are using bulk logic with save exceptions to open the cursor and load the data into the target table.
I have a SQL query where I am making UNION of two select statements. The table that I am joining in each select statement have indexes defined for those tables.
Now the UNION of the two select statements again in enclosed in an inline view , from which I fetching my final field values.
The select statements inside the inline view returns huge number of row (like 50 million rows).
The whole query fails with time out.
Is there a way to pass Oracle Hints so that Oracle uses indexes?
In my code I am using delete statement which is taking too much time to execute.
Statement is as follow:
DELETE FROM TRADE_ORDER_EMP_ALLOCATION T WHERE (ARTEMIS_SOURCE_SYSTEM_ID,NM_ARTEMIS_SOURCE_SYSTEM,CD_BOOK_KEY,ACTIVITY_DT) IN (SELECT ARTEMIS_SOURCE_SYSTEM_ID,NM_ARTEMIS_SOURCE_SYSTEM,CD_BOOK_KEY,ACTIVITY_DT FROM LOAD_TRADE_ORDER WHERE IND_IS_BAD_RECORD='N');
Every column in "IN" clause and select clause is containing index on it
Every time no of rows which to be deleted is vary (May be in hundred ,thousand or hundred thousand )so that I am Unable to use "BITMAP" index on the table "LOAD_TRADE_ORDER" column "IND_IS_BAD_RECORD" though it is containing distinct record in it.
Even table "TRADE_ORDER_EMP_ALLOCATION" is containing "RANGE" PARTITION over it on the column "ARTEMIS_SOURCE_SYSTEM_ID". With this I am enclosing table scripts with Indexes and Partitions over it.
way for fast execution in of above delete statement?
My oracle database version is 11.2.0.3.0 where i am having one schema in that schema i am having 3 same tables with same structure same data but with different name.
but problem is in first table when i perform select query it takes 5 sec, in another table it is taking 0 sec and in third table it is taking 10 sec.
I have been told that i should use multiple's of 4 as degree in the parallel hint to get maximum performance, so i am wondering is it true? that i should always use multiples of 4 or i can use any number inside the parallel hint.
and the rest of those are small tables..All the indexes are in place and I have tried with few hints but this query is slow.
WITH REPS AS (SELECT DISTINCT REP_SET.FILTER_TOKEN FROM (SELECT /*+ INDEX (wdsd WEBDATASETDTL_PK_TEAM) */ DISTINCT WDSD.DATA_SETTING_ID, WDSD.FILTER_TOKEN FROM WEB_DATA_SETTING_DETAIL WDSD, [code]....
If we have not set parallel degree for a table then we can ( try to ) force parallel execution on a table using a parallel hint Does this 'parallelism' works on the index search in the query as well?
In which situations non-parallel non-partitioned table but parallel index (degree>2) will facilitate a query?
I have a query with FULL hint that is behaving in a strange manner. The query fetches around 700000 of data. Sometimes it fetches the data with the hint and sometimes it does not fetch any data with the hint and then I have to remove the hint and have to fetch the data. Below is the query,
Our application servers will be running a SELECT which returns zero rows all the time.This SELECT is put into a package and this package will be called by application servers very frequently which is causing unnecessary CPU.
Original query and plan
SQL> SELECT SEGMENT_JOB_ID, SEGMENT_SET_JOB_ID, SEGMENT_ID, TARGET_VERSION FROM AIMUSER.SEGMENT_JOBS WHERE SEGMENT_JOB_ID NOT IN (SELECT SEGMENT_JOB_ID FROM AIMUSER.SEGMENT_JOBS) 2 3 4 5 ; [code]....
Which option will be better or do we have other options?They need to pass the column's with zero rows to a ref cursor.
I have a Query(report) which is running in <5 mins in one Scheme, where as the same is running for a long time in second schema. I have identified that an Index is scanning for more than 2000 Millions of records in second Schema, but this is scanning only 440 Millions in First Schema and hence it is fast. I am expecting the same to be done in Second schema.
I have verified the following All records in tables in 2 schemas are same. All indexes are same Analyzed the tables Gathered Histogram on all the columns as per the first schema.
But now i still have the same problem, don't know what could be the problem.
I have an APP that truncates tables and loads data, which in turn makes the stats stale. I ran the query advisor (see attachment) and of course it ecommends running stats or accept a profile.I really don't want to do that as it may cause a load on my DB.
In turn, I would like to consider having my APP team change the query to pass a hint to use the best query plan.syntax to pass the hint to emulate good attached plan? Or is this a bad way to proceed?
select /* INDEX FAST FULL SCAN PK_PLACEMENT_REQUEST_QUEUE */ sum(lastshares) as "ROSEN" from nyeo.fix_exec_reports fer, nyeo.placement_request_queue q, nyeo.nyeo_block_control bc where fer.clordid = q.sequence_number and q.blockid = bc.blockid and upper(bc.deskname) like '%ROSEN%'
I wish to run a SQL query and measure elapsed time, then compare the values to other Oracle DBs from other companies. That will give me a feeling if our DB performs well.For example in UNIX world, you can create a random 4GB file to measure throughput I/O and compare the values (for example 4MB/sec).
What's the simplest way to compare DB response time from forum members to our own DB? I don't need 100% accurate numbers.
I am inserting data into a global temporary table and then using 'parallel' hint to query from this temporary table. I remember reading that the queries on the temp table may not run in parallel as the parallel sessions may not be able to see the data in the temporary table
However the execution plan as well as px_session, v$sql indicate that the query on the temporary table in fact run in parallel mode
select * from table(dbms_xplan.display_cursor(null,null,'ALLSTATS LAST'));
PLAN_TABLE_OUTPUT ----------------------------------------------------------------------------------------------------------------------- SQL_ID 7d68g52g0mskz, child number 0 ------------------------------------- select /*+ gather_plan_statistics parallel(t,4) */ * from dbo_gtt t order by id,object_id
I am writing below MERGE statement. In this cardinality between table_a and table_b is 1:2. I.e. each record in table_b corresponds to 2 records in table_a based on columns in ON clause.
Well this query throws below error.
----Error---
ORA-12801: error signaled in parallel query server P011
ORA-30926: unable to get a stable set of rows in the source tables
However, the same statement executes successfully when PARALLEL hint is removed altogether. (There are no duplicates in table_b based on unit,group,loc columns.)
-----Query--------
MERGE /*+ PARALLEL(8) */ INTO table_a a USING table_b b ON (a.unit = b.unit AND a.group = b.group AND a.loc = b.loc)
I am executing a sql statement which is doing FTS in parallel mode The server has 8 cpus and threads_per_cpu is 2
The v$sql shows PX_SERVERS_EXECUTIONS as 8
select PX_SERVERS_EXECUTIONS, sql_text from v$sql where sql_id='0q0nk5117yth2' 8, select /*+ full(a) parallel(a)....
however the px_sessions shows 17 sessions (16 parallel session + 1 parent session (where sid = qcsid) Now in px_sessions, these 16 parallel session are divided in 2 server sets 1 and 2 and values for degree and required degree are 8 and 16 respectively
However, all the time, only 8 sessions which belong to server set = 1, were active though its state was waiting with event "PX Deq Credit: send blkd"
The other session which belong to server set = 2 were never active and always had waint event ='PX Deq: Execution Msg'
what could be the reason that 16 parallel session could not be started though I am the only person using the server, there aren't any batch jobs, dbms_jobs,even archivelogs (not a prod system)?
Note that paralel_max_servers setting is 16
Another issue being the duing start of the query approximately 100-115 blocks were read for the query (checked from longops) however after 60-70% blocks are read the number of blocks read / seconds falls down to 10-20 blocks / second across all parallel sessions.
I want to know how I can find which query is taking more time , for example some query's are run from unix, java and from toad,sqlplus. and one query is taking much more time to execute, so how i can get that query and all the details.
I have a query which is executing fast in dev env,but very long time in qa env.What is the criteria when this behaviour occurs.Though qa is having more data than dev.But still it is taking long time for 1 rows also.When I am using the query rownum<=1.So What to check for this.
During batch process record is entered in detail table as well as summary table.
The process first checks if record exists in summary table for same group_no and if 'yes' then "updates" the record with the newly added amount (sums it) else inserts a new record Whereas in the detail table it inserts the record directly
Now if the batch process runs in parallel, (out of many) two different sessions insert same group_no; This is because while sesond session inserts a record, first session inserting the same record (group_no) has not yet committed ; So second session Not knowing that already there is same Group_no (101) inserted, again inserts another record with same group_no rather than summing it.
Can it be solved without using temp table, select for update?
I have a question about database fragmentation.I know that fragmentation can reduce performance in query times. The blocks are distributed in many extents and scans process takes a long time. Oracle engine have to locate the address of the next extent..
I want to know if there is any system view in which you can check if your table or index has high fragmentation. If it's needed I will have to re-create, move or rebulid the table or index, but before I want to know if the degree of fragmentation is high.
Any useful script or query to do this, any interesting oracle system view?
Somewhere I read that we should not use hints in Oracle production environments, but we can use hints in the development environment and on achieving the desired execution plan we can adjust the 'statistics' to follow that plan without hints.
Q1. If it is true what statistics do we adjust for influencing the execution plan and how?
For example, I have the following simple query:
select e.empid, e.ename, d.dname from emp e, dept d where e.deptno=d.deptno;
emp.empid, emp.deptno and dep.deptno columns have indexes and the tables have the standard structure as found in the basic oracle examples.
If I look at the execution plan of the above query then I see that the driving table is empand the driven table is dept.Also the type of join that is taking place is 'Nested Loop'.
Questions: With respect to the above query, Q 2. If I want to make dept the driving table and emp the driven table then how can I adjust the statistics to achieve that? Q 3. If I want to use hash join instead of a nested loop join then then how can I adjust the statistics to achieve that?
I can put the ordered and the use_hash hint to effect this but again I have heard that altering statistics is a more robust way to control an execution plan as compared to hints.
