RE: insert /*+APPEND*/ Unexpected result (more redo log)

From: Nick Wagner <Nick.Wagner_at_quest.com>
Date: Tue, 06 May 2003 09:32:02 -0800
Message-ID: <F001.005914D7.20030506093202@fatcity.com>

it looks as though when using an /*+APPEND*/ hint, that Oracle still does QMI (array inserts) but each array only contains one or two rows...  

Run a report of the actual space used in the table, compared to the amount specified by PCTFREE and you'll see that the actual used space is very low. Check the number of extents on the two tables as well. Also with QMI, Oracle writes additional information to the redo log about the block, and any rowids contained within it. So you are writing out many more redo log blocks than necessary when doing an APPEND.  

I'm guessing that with your configuration, that about 12-14 rows of ALL_OBJECTS will fit in a single DB_BLOCK...  

-----Original Message-----
Sent: Tuesday, May 06, 2003 9:52 AM
To: Multiple recipients of list ORACLE-L

try  

alter table redolog_test nologging;  

before the insert append

-----Original Message-----
Sent: Tuesday, May 06, 2003 9:52 AM
To: Multiple recipients of list ORACLE-L

Hi All,

I'm getting UNEXPECTED result in both 8i and 9iR2.

Could someone please tell me why insert /*+APPEND*/ generates more redo log.

I'm pretty sure that there is NO index involved in my test table(redolog_test).
Also the user is not a SYS and SYSTEM.
The DB is running in ARCHIVE LOG mode.

SQL> show user
USER is "MUT"

SQL> drop table redolog_test;
Table dropped.

SQL> create table redolog_test pctfree 99 pctused 1 as select * from all_objects
where 1=2;
Table created.

SQL> insert into redolog_test select * from all_objects; 19412 rows created.

Statistics

---

       2003  recursive calls 
      89992  db block gets 
     161720  consistent gets 
          0  physical reads 
   10661144  redo size  <======== 
        438  bytes sent via SQL*Net to client 
        433  bytes received via SQL*Net from client 
          4  SQL*Net roundtrips to/from client 
          2  sorts (memory) 
          0  sorts (disk) 
      19412  rows processed 

SQL> truncate table redolog_test;
Table truncated.

SQL> insert /*+APPEND*/ into redolog_test select * from all_objects; 19412 rows created.

Statistics

---

       2012  recursive calls 
        365  db block gets 
     142229  consistent gets 
          0  physical reads 
  159534376  redo size  <=======(15 Times higher) 
        430  bytes sent via SQL*Net to client 
        445  bytes received via SQL*Net from client 
          4  SQL*Net roundtrips to/from client 
          2  sorts (memory) 
          0  sorts (disk) 
      19412  rows processed 

SQL> What could be wrong?

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--

Author: Nick Wagner
  INET: Nick.Wagner_at_quest.com

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