If we insert a row in a database table then the new row stays at database buffer cache in SGA (until commit), right?. The target table is not affected (before commit). The new row is saved after commit.
I saw a concepts at Sybex oracle 10g oca book (Page 406) as follows:
" INSERT statements use little space in an undo segment; only the pointer to the new row is stored in the undo tablespace. To undo an INSERT statement, the pointer locates the new row and deletes it from the table if the transaction is rolled back. "
My question is If the row is not saved at table before commit, if we issue rollback then how oracle delete from table? I think the new row is deleted from database buffer cache in SGA.
how to insert data in oracle table without writing insert statement in oracle 9i or above. i am not going to write insert all, merge, sqlloder and import data.
The view that can be used to find the changes the plans (hash_value,plan_hash_value for a particular sql statement).
I have a particular sql statement for which the execution plan changes but, unfortunately i cannot find regarding which view can be used to find the details regarding this. V$SQL_PLAN_MONITOR is not working as well.
I have queries on the execution plan of a sql statement
Following is the example
create table t1 as select s1.nextval id,a.* from dba_objects a; create table t2 as select s2.nextval id,a.* from dba_objects a; insert into t1 select s1.nextval id,a.* from dba_objects a; insert into t1 select s1.nextval id,a.* from dba_objects a; insert into t2 select s2.nextval id,a.* from dba_objects a; insert into t2 select s2.nextval id,a.* from dba_objects a; insert into t2 select s2.nextval id,a.* from dba_objects a; commit;
create index i1 on t1(id); create index i2 on t2(id); create index i11 on t1(object_type);
(1) First index on object_type is accessed to get rowids - t1.object_type='VIEW' (2) Then the filter on owner is applied - t1.owner='SYS' (3) Then the table T1 is accessed to fetch data from the rowids returned by the index I11 and filer application - TABLE ACCESS BY INDEX ROWID
Though I am unable to understand how filter can be applied to the rowids retrieved from index, we can see from the plan below that The rows accessed have reduced from 8550 to 1221 before we access the table...Thus filter "t1.owner='SYS'" is applied in between. Right?
another question is
Case 1 - do we retrieve a rowid from index for a given value, then retrieve required values from table for that rowid Thus row at a time in both ... in loop OR Case 2 - we first fetch all rowids from index and then retrieve values from table one row at a time from the collection of rowids fetched?
Suppose Case 1 is what is happening then can we say, both the steps mentioned by IDS 2,3 in plan below are executed exactly equal number of times and the filter "t1.owner='SYS'" is applied at some later stage? Of course in this case the values in ROWS stand misleading then
select * from t1,t2 where t1.id = t2.id and t1.object_type='VIEW' and t1.owner='SYS';
Execution Plan ---------------------------------------------------------- Plan hash value: 26873579 ------------------------------------------------------------------------------------- | Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | ------------------------------------------------------------------------------------- | 0 | SELECT STATEMENT | | 1221 | 233K| 915 (1)| 00:00:11 | |* 1 | HASH JOIN | | 1221 | 233K| 915 (1)| 00:00:11 | |* 2 | TABLE ACCESS BY INDEX ROWID| T1 | 1221 | 116K| 381 (1)| 00:00:05 | |* 3 | INDEX RANGE SCAN | I11 | 8550 | | 24 (0)| 00:00:01 | | 4 | TABLE ACCESS FULL | T2 | 161K| 15M| 533 (1)| 00:00:07 | ------------------------------------------------------------------------------------- Predicate Information (identified by operation id): --------------------------------------------------- 1 - access("T1"."ID"="T2"."ID") 2 - filter("T1"."OWNER"='SYS') 3 - access("T1"."OBJECT_TYPE"='VIEW')
1. In previous version of Toad (9.7.2) during executing a statement I was able to click on 'Explain plan current statement'. In this version of Toad (10.6.0. 42) is not a possible to do it.In the Toad options I've filled the sign: "use a separate connection when Toad itself is generating transactions"
2. During executing a statement I still see 'clock' cursor.Is it a possible to disable to see it?
Session 1 create table tab1 as select * from dba_objects where object_id is not null; alter session set events '10046 trace name context forever, level 12'; declare x number; begin for i in 1..4 loop
[code]....
Session 2
after "starting" the above pl/sql block from Session 1, I keep on querying tab2 from Session 2 And as soon as 2 records are inserted in tab2, I create index from Session 2
select * from tab2; select * from tab2; select * from tab2; N ---------- 1 2 create index i on tab1(object_id);
As I have tested from a single session (just before this test) such index is used for the sql statement
select count(1) into x from tab1 where object_id=2331;
However when I checked the trace file I am not geeting results as expected
I am expecting 4 execution plans - 2 FTS and 2 Index Access scans and for this I am issuing following command
SELECT COUNT(1) FROM TAB1 WHERE OBJECT_ID=2331 call count cpu elapsed disk query current rows ------- ------ -------- ---------- ---------- ---------- ---------- ---------- Parse 1 0.00 0.00 0 1 0 0 Execute 4 0.00 0.00 0 2 0 0
[code]....
1) Why I am unable to see 4 execution plans - 2 with FTS and 2 with Index access when I mentioned 'aggregate=no'?
2) Whether the index i will be used for last 2 iterations after first 2 iterations of FTS?
If answer to above question 2) is 'No'
By which method I can force an ongoing sql statement in loop to take different execution path? Of course I can't hard parse sql in 'that' current session Will flushing Shared pool work in above case?
Is there any way to find out the division between the time taken for query parsing, creating execution plan and actual data retrieval seperately? If I enable 'set timing on' I see the elapsed time which is the total time taken for all these 3. Some of my queries are taking long time when I run it first time and so want to know what is it taking long? is it the parsing or creating the execution plan, if so what can I optimize.
I am trying to find the unix process for one of my application in the database but I am unable to view the same. To simulate, I did the following.
1. My database runs on different server. 2. I invoked "sqlplus" from another unix box to login to the database. 3. I found that the process id (ps -ef |grep sqlplus). 4. When I execute the below mentioned query it does not display the process id that I am looking for. But the osuser, username, program and machine details are correct. How can I know the process details from the database?
SELECT SYS.GV_$SESSION.OSUSER, SYS.GV_$SESSION.USERNAME, SYS.GV_$PROCESS.SPID, SYS.GV_$SESSION.MACHINE, SYS.GV_$SESSION.PROGRAM, SYS.GV_$PROCESS.PROGRAM ,SYS.GV_$SESSION.SQL_ID FROM SYS.GV_$PROCESS, SYS.GV_$SESSION WHERE SYS.GV_$PROCESS.ADDR=SYS.GV_$SESSION.PADDR and SYS.GV_$SESSION.USERNAME='TEST' and SYS.GV_$SESSION.MACHINE like '%hostname%'
We performed image copy of production Oracle server (OS and instances) to a backup server. After a few weeks, we try to restore a latest Oracle database backup from production server to backup server. As we know, Oracle instance must be unique on the network.
Even we log on to backup server and bring up the instance, I think that still point to production instance since all init file, TNSNAMES.ora and listener file are still same. If we restore the database, we will end up bring down the production instance and restore on top of productions. How to change instance name on backup server including TNSNAMES, sqlnet, listener files in order for us to restore Oracle database from production to backup server?
Whenever any transaction happen in database redo has generated for this transaction. Do select statement treat as a transaction as it doesn't modify any thing in database. And If select statement should not be a transaction, there should not be any redo generation for select statement.
So is select statement generate redo? If yes then Why ?
I am having database A and database B and I am inserting into database b by selecting some records from database a using db link.Is there any way to find whether database link is being used?
We need to find when any datafile was resized ( if at all)in a tablespace. Actually, by noting the created date from v$datafile , we used to know the data growth in a tablespace. Now as the number of datafiles have increased, we want to resize them. This diagnostinc have to be done without changing/adding anything in DB.
where i can find an alert log errors so whenever they occur in my RAC so i can comprehend them very well. I am trying to know that what can be the errors when u have RAC with ASM and SAN .
I am trying to record audit info about sql statement run by user (only one audit entry per specific type of operation such as create table, or insert table). Such as if a user create three tables, but database record only one entry of create table type per session.
I am giving you all the statement I issued...
SQL> create user saimon identified by abc1;
User created.
SQL> grant connect, resource to saimon;
Grant succeeded.
SQL> audit table, insert table by saimon by session;
Audit succeeded.
SQL> show parameter audit
NAME TYPE VALUE -------------------- ----------- ------------- audit_file_dest string /u01/app/oracle/admin/orcl/adum audit_sys_operations boolean FALSE audit_syslog_level string audit_trail string DBSQL>
[oracle@DBTEST ~]$ sqlplus saimon/abc1
SQL*Plus: Release 10.2.0.1.0 - Production on Thu Jul 19 21:45:09 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production With the Partitioning, OLAP and Data Mining options
SQL>
SQL> create table TB1 (id number, name varchar2(20));
Table created.
SQL> create table TB3 (id number, name varchar2(20));
Now my question is I have enabled statement auditing for session not by access. So only one audit entry should have been recorded for two table creation. Why database is recording every create statement?
SQL> show user USER is "SYS"
SQL> SELECT audit_option, failure, success, user_name 2 FROM dba_stmt_audit_opts;
AUDIT_OPTION FAILURE SUCCESS USER_NAME ----------------------------------- ---------- ---------- ------------------------------ TABLE BY SESSION BY SESSION SAIMON INSERT TABLE BY SESSION BY SESSION SAIMON
the most accurate/efficient way of obtaining the execution plan for a piece of running SQL in Oracle 9i. in 10g and 11g obviously dbms_xplan.display_cursor(sql_id) can be used,
How can this be achieved in 9i, currently I am simply obtaining the SQL_TEXT and then running an explain plan ("EXPLAIN PLAN FOR..") - I believe this is not necessarily the same explain plan that will be used for the sql that is executing though
I am getting below ORA-01555 error in alert log everyday.
ORA-01555 caused by SQL statement below (SCN: 0x09ad.86a4562a): Sat Jan 21 08:39:45 2012 SELECT (NVL(MAX(BLOCK_ID + BLOCKS ),0) * :b1 ) / 1024 FROM DBA_EXTENTS WHERE TABLESPACE_NAME = :b2 AND FILE_ID = :b3
I cannot able to find the sql_id here. So how can I find from which process or session this query is firing? before increasing the undo size, I need to analyze as why it is occuring?
