PL/SQL :: Created Partition And Parallel Degree 4 On Table A
Oct 10, 2012
I have table A with size 120 Million and two more tables are of size 2 Million on Table B and less than 1 Million size on table C.I had created Partition and Parallel degree 4 on the table A. Created table B with Parallel degree 2 and Created table C with NOPARALLEL.
My query is using above tables with joins and inserting into table D using HINT /*+ APPEND NOLOGGING*/I had executed the explain on the above criteria the cost is showing 20767.
Later created Tables A,B and C with NOPARALLEL. Applied HINT on Table D /*+ APPEND NOLOGGING*/ and als applied HINT /*+ PARALLEL(A, 4) PARALLEL(B C, 2) on select query which uses to insert into Table D.
My question which is best practice on PARALLEL degree creation at table level or query level:
a) Creating table with Paralle (degree 4)
b) Applying HINT /*+ PARALLEL (TABLE A , 4) */ at query level
I am inserting 50 million records into a table MAIL_LOG. I am using the hint /*+ append parallel (MAIL_LOG, 12) */. But for my table degree is 1.
SELECT table_name, degree FROM user_tables WHERE table_name = 'MAIL_LOG';
I have following clarifications. 1) What degree I should use. 2) On what basis I have to give the degree. 3) Have we use constant degree all the times. 4) How to check my insert statement is using parallel degree. 5) How to find the degree at session level.
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.
In my recent performance improvement tasks I was experimenting with Parallel hints. I have been getting good results with them, however the question arises "How is Parallel degree proportionate to number of CPUs used during execution?
/*+ parallel(emp_tab,8) */ Oracle Version: Oracle 10g OS : UNIX Client OS: Windows XP V$PARAMETER VARIABLES as follows: Total CPUs available: 10 No of CPUs per core: 2 Max parallel : 100 Min Parallel : 5
Question 1: So how do I map the degree of 8 with CPUs. I believe that degree of 8 does not mean its going to use 8 CPUs. If so, how do I prove it. I tried SQL_TRACE and cpu comes 0. And I believe its not the CPU count.
Question2: How do I know how many CPUs were used to execute a SQL query ?
I am executing a sql statement which is doing FTS in parallel mode The server has 8 cpus and threads_per_cpu is 2
The v$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 have created an another instance on a single machine i got error when starting up a new one - error starting up database in exclusive mode so i shutdown older database instance , to start new one now is it possible to run both instance parallel?
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 one table and I created partition month wise. I also creates index on that table. How can I check whether parition will be used when I query that table? In explain plan I can see PARTITION RANGE as ALL. Is it using the partition?
I think that performance better partition table than non-partition table. How to assure partition table is better than non-partition table at SELECT operation?
I have compare a specific query EXPLAIN PLAN at partition table and non-partition table. both tables data is same. Is it true way or not?
I have a table that partitioned into six partitions. each partitions placed in different table space and every two table space placed it on a different hardisk
when I will do query select with the non-partition keys condition, how the search process ? whether the sequence (scan sequentially from partition 1 to partition 6) or partition in a hardisk is accessed at the same time with other partition in other hardisk. ( in the image, partition 1,4 accessed at the same time with partition 2,5 and 3,6)
Can i alter the table to create partition on non partition table, i have tried and could not create it. Do we have some other means to do it as this is the live table and cannot drop them else will lose the data.
Can I add range sub partition to a hash partition table. Example like this.
CREATE TABLE test ( test_id VARCHAR2(10 ) , test_TYPE VARCHAR2(5) , CREATE_DATE date ) partition by hash (test_id, test_type) Partitions 3 SUBPARTITION BY RANGE (CREATE_DATE);
When Tried, I am getting syntax error as invalid option.
When I am trying to insert record from tbl_mittal into tbl_temp table. I am facing "ORA-14400: inserted partition key does not map to any partition" error
SQL> insert into tbl_temp select * from tbl_mittal; insert into tbl_temp select * from tbl_mittal * ERROR at line 1: ORA-14400: inserted partition key does not map to any partition
AS tbl_mittal is having hugh number of records so I am providing only few rows from tbl_mittal table as test data.
How to find the size pf a partition in a partition table?I guess we need to query views like dba_tab_partitions but I am not very sure. will running dbms_stats.gather_table_stats('schema_name,'table_name,'partition_name')
There is an index with degree 16 on a rac env. The base table has no degree. The table and index are not partitioned. Does the degree of index only affect index DDL (alter, rebuild etc)? Any effects on query (PQ)?
At work we have a linux server with Oracle 10.2.0.5 g, and we have the need, to save time, to use parallel process launched in background (&) or (at now).
The table that we are going to insert is partitioned for date and subpartitioned for name of file_source, and we are having a lot of problem with this.
Our DBA staff say that is impossible to work in this way but for me, after ten year of oracle-work, sounds strange , sure may be that we don'r use really really correctly this procedure but i suppose that Oracle is able to recevie 20 ask of insert on the same table.
The situation is that we usede this procedure in other server and it's work but the answer of our DBA-staff is that we have less data storage and so on. In the end some times this proceduers have a low time of execution and some times no, this goes out of my ability to find out the problem.
We have a DWH with STAGING AREA, ODS Level, DDS Level and DM Level, the Staing area is paritionend for file_source, the ODS Area is partitioned by range (date) and subpartitioned for name (file_source), the DDS area is partitioned by range(date) and subpartitioned for Origin system(that include all the file_source) and the DM area is only partitioned by date.
So the most big problems that we meet are between the Staging are and ODS area, and between the Ods area and the DDS Area, the most important thing is that this table (DDS) is a monster of near 500.000.000 of rows (ITr of data) but we look only at the date to elaborate.
The solution is clear, divide this table in two, one online and one of storage as usually and correctly a normal situation require, but unfortunatly is a situation that we Erhedit from an old system and at the moment is not approoved the change request on this site.
The really strange thing is that sometimes work and some times not, without understand the cause of this. My opinion on this is that the DB is not correctly configured but the System Staff say that everything is correct and there are no problem. My first problem is to understand, if possible, wich is the limit of this way to operate, can i insert in a subpartition in the same time with twenty parallel process that write on same partition and different subpartition? Is correct to act in this way to save time about the data-load or better doing it one by one? On my experience i realized that Oracle can manage(is his work) a lot of request in the same time, but in this DB that we are using i continue to see problems that sounds like if we are usuing a tool that is not working in the correct way...
May be we went beyond some limit but in the end are less then 5.000.000 records per day that we move i think that a DWH have to support more than this...
If multiple queries are run in parallel(at the same time) against a table or a set of tables (query referencing multiple tables), does it reduce the performance.
In other words is Oracle capable of reading (selecting from) the same table multiple times in parllel.
I think that performance better partition table than non-partition table. How to assure partition table is better than non-partition table at SELECT operation?
I have compare a specific query EXPLAIN PLAN at partition table and non-partition table. both tables data is same. Is it true way or not?
'Oracle fast parallel data unload into ASCII file(s)' in this blog: URL....I have compiled the code and created the objects and the directory in my DB...But when I execute :
SELECT * FROM TABLE( DATA_UNLOAD( CURSOR( SELECT /*+ PARALLEL(A, 2, 1) */ TABLE_NAME || '|' || COLUMN_NAME || '|' || DATA_TYPE FROM MYTABLE A [code]....
It is supposed to return 2 rows (because of parallel execution), but it just returns 1..Do I have to do something special in order to make parallel pipelined function work
I am trying to add partition to table without partition
with following code
ALTER TABLE ACC_LOC1_TAB ADD PARTITION testpart BY RANGE (ALT_AUTHDT) (PARTITION UPTO_2010 values less than (31-mar-2010), PARTITION APR_JUN_10 VALUES less than (30-JUN-2010), PARTITION JUL_SEP_10 VALUES less than (30-SEP-2010), PARTITION OCT_DEC_10 VALUES less than (31-DEC-2010), PARTITION JAN_MAR_11 VALUES less than (31-MAR-2011))
I am using Oracle 11.2.0.1 Oracle Database.I have a table with 10 Million records and it's a Non Partitioned Table.
1) I would like to partition the table (with partition by range ) without creating new table . I should do it in the existing table itself (not sure DBMS_ REDEFINITION is the only option ) (or) can i use alter table ...?
2) Add one partition which will have data for the unspecified range.
i have table with range partition and list sub-partition..can i add one more list sub-partition if it is not possible , i have to drop first sub-partition.
