There is a note in Metalink that explains that on Windows having space characters in your ORACLE_HOME variable, the patch location or JDK location causes an error when running opatch. Yesterday I saw a strange problem that is similar to the above case.
If your opatch directory contains space characters you get a strange error. Even if the above conditions were not present we got an error like this:
C:\Documents and Settings\test\Desktop\OPatch>opatch lsinventory
Exception in thread "main" java.lang.NoClassDefFoundError: and
OPatch failed with error code = 1
Metalink returns no results for this error. This error is caused by the space characters in "Documents and Settings". When you move the opatch directory to another directory which does not contain space in its name opatch runs without this problem.
Just a note to help in case someone gets the same error.
Friday, June 19, 2009
opatch problem on Windows
DBFS
Yesterday I attended Kevin Closson's Exadata technical deep dive webcast series part 4. It is now available to download here. In there he talks about DBFS which is a filesystem on top of the Oracle database which can store normal files like text files. DBFS is provided with Exadata and is used to store staging files for the ETL/ELT process. This looks very promising, he sites several tests he conducted and gives performance numbers too. Watch the webcast if you haven't yet.
Tuesday, June 09, 2009
Tablespace selection in interval partitioning
11G brought interval partitioning which is a new partitioning method to ease the maintenance burden of adding new partitions manually. The interval partition clause in the create table statement has an option to list tablespace names to be used for interval partitioning. The documentation states that the tablespaces in the list you provide are used in a round-robin manner for new partitions:
Interval partitions are created in the provided list of tablespaces in a round-robin manner.
This does not mean that any newly created partition will reside in the tablespace which is next on the list. The tablespaces may be skipped if partitions map to more than one interval. Here is a test case that shows how the list is used.
set lines 200
SQL> r
1 create table t(col1 date,col2 varchar2(100))
2 partition by range (col1)
3 interval(numtoyminterval(1,'MONTH')) store in (tbs1,tbs2,tbs3)
4* (PARTITION p0 VALUES LESS THAN (TO_DATE('1-1-2009', 'DD-MM-YYYY')) tablespace tbs1)
Table created.
SQL> r
1 select PARTITION_NAME,HIGH_VALUE,TABLESPACE_NAME
2* from user_Tab_partitions where table_name='T'
PARTITION_NAME HIGH_VALUE TABLESPACE_NAME
------------------------------ -------------------------------------------------------------------------------- ------------------------------
P0 TO_DATE(' 2009-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS1
The "store in" clause lists tablespaces tbs1, tbs2 and tbs3 to be used for interval partitioning. After the above create table command I now have one partition which resides in tbs1. Let's insert a row which needs to be inserted into a new partition and see which tablespace the partition will be created in.
SQL> insert into t values(to_date('15.01.2009','dd.mm.yyyy'),'jan');
1 row created.
SQL> commit;
Commit complete.
SQL> select PARTITION_NAME,HIGH_VALUE,TABLESPACE_NAME
2 from user_Tab_partitions where table_name='T';
PARTITION_NAME HIGH_VALUE TABLESPACE_NAME
------------------------------ -------------------------------------------------------------------------------- ------------------------------
P0 TO_DATE(' 2009-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS1
SYS_P61 TO_DATE(' 2009-02-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS2
The row I inserted maps to one interval, which is one month, it does not have a date value which is more than one month higher than the current maximum value. So the next tablespace, tbs2, is used for the new partition.
SQL> insert into t values(to_date('15.02.2009','dd.mm.yyyy'),'feb');
1 row created.
SQL> commit;
Commit complete.
SQL> select PARTITION_NAME,HIGH_VALUE,TABLESPACE_NAME
2 from user_Tab_partitions where table_name='T';
PARTITION_NAME HIGH_VALUE TABLESPACE_NAME
------------------------------ -------------------------------------------------------------------------------- ------------------------------
SYS_P62 TO_DATE(' 2009-03-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS3
P0 TO_DATE(' 2009-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS1
SYS_P61 TO_DATE(' 2009-02-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS2
Again I inserted a row for the next month and the partition is created in tbs3, which is the next one on the list.
What happens if I insert a row with a date value that is more than one month after the current maximum partitioning key?
SQL> insert into t values(to_date('15.04.2009','dd.mm.yyyy'),'apr');
1 row created.
SQL> commit;
Commit complete.
SQL> select PARTITION_NAME,HIGH_VALUE,TABLESPACE_NAME
2 from user_Tab_partitions where table_name='T';
PARTITION_NAME HIGH_VALUE TABLESPACE_NAME
------------------------------ -------------------------------------------------------------------------------- ------------------------------
SYS_P62 TO_DATE(' 2009-03-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS3
P0 TO_DATE(' 2009-01-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS1
SYS_P61 TO_DATE(' 2009-02-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS2
SYS_P63 TO_DATE(' 2009-05-01 00:00:00', 'SYYYY-MM-DD HH24:MI:SS', 'NLS_CALENDAR=GREGORIA TBS2
I skipped March and inserted a value for April. The current maximum key becomes May 1st, we do not see a partition with a maximum value of Apr 1st. The next tablespace on the list was tbs1 but we see that the new partition is on tbs2, not tbs1. Tbs1 would be used if I did not skip an interval when inserting rows.
So, the tablespaces on the list are used in a round-robin manner but each is used for only one interval. If you skip intervals the tablespaces related to that interval are skipped too.
This is something to keep in mind if you want to strictly decide which tablespace will hold which partition.
Wednesday, March 04, 2009
Different plans for a sql with the rule hint
I was trying to find out why a query with the RULE hint produces different plans. I got stuck so I posted the problem to the OTN database forum and Randolf Geist provided a good answer and starting point for it. A second eye on the problem can remove the mind blockage and clear your way.
Monday, February 23, 2009
Remote dependencies
When changing plsql code in a production system the dependencies between objects can cause some programs to be invalidated. Making sure all programs are valid before opening the system to users is very important for application availability. Oracle automatically compiles invalid programs on their first execution, but a successfull compilation may not be possible because the error may need code correction or the compilation may cause library cache locks when applications are running.
Dependencies between plsql programs residing in the same database are easy to handle. When you compile a program the programs dependent on that one are invalidated right away and we can see the invalid programs and compile or correct them before opening the system to the users.
If you have db links and if your plsql programs are dependent on programs residing in other databases you have a problem handling the invalidations. There is an initialization parameter named remote_dependencies_mode that handles this dependency management. If it is set to TIMESTAMP the timestamp of the local program is compared to that of the remote program. If the remote program's timestamp is more recent than the local program, the local program is invalidated in the first run. If the parameter is set to SIGNATURE the remote program's signature (number and types of parameters, subprogram names, etc...) is checked, if there has been a change the local program is invalidated in the first run.
The problem here is; if you change the remote program's signature or timestamp you cannot see that the local program is invalidated because it will wait for the first execution to be invalidated. If you open the system to the users before correcting this you may face a serious application problem leading to downtime.
Here is a simple test case to see the problem.
I start by creating a plsql package in the database TEST.
SQL> create package test_pack as
2 procedure test_proc(a number);
3 end;
4 /
Package created.
SQL> create package body test_pack as
2 procedure test_proc(a number) is
3 begin
4 null;
5 end;
6 end;
7 /
Package body created.
On another database let's create a database link pointing to the remote database TEST, create a synonym for the remote package and create a local package calling the remote one.
SQL> create database link test.world connect to yas identified by yas using 'TEST';
Database link created.
SQL> select * from dual@yas.world;
D
-
X
SQL> create synonym test_pack for test_pack@yasbs.world;
Synonym created.
SQL> create package local_pack as
2 procedure local_test(a number);
3 end;
4 /
Package created.
SQL> r
1 create or replace package body local_pack as
2 procedure local_test(a number) is
3 begin
4 test_pack.test_proc(1);
5 end;
6* end;
Package body created.
If we look at the status of this local package we see that it is valid.
SQL> col object_name format a30
SQL> r
1* select status,object_name,object_type from user_objects where object_name='LOCAL_PACK'
STATUS OBJECT_NAME OBJECT_TYPE
------- ------------------------------ ------------------
VALID LOCAL_PACK PACKAGE
VALID LOCAL_PACK PACKAGE BODY
We can execute it without any problems.
SQL> exec LOCAL_PACK.local_test(1);
PL/SQL procedure successfully completed.
Now, let's change the remote package code including the package specification.
SQL> create or replace package test_pack as
2 procedure test_proc(b number,a number default 1);
3 end;
4 /
Package created.
SQL> create or replace package body test_pack as
2 procedure test_proc(b number,a number default 1) is
3 begin
4 null;
5 end;
6 end;
7 /
Package body created.
When we look at the local package we see its status as valid.
SQL> r
1* select status,object_name,object_type from user_objects where object_name='LOCAL_PACK'
STATUS OBJECT_NAME OBJECT_TYPE
------- ------------------------------ ------------------
VALID LOCAL_PACK PACKAGE
VALID LOCAL_PACK PACKAGE BODY
But when it is executed we get an error.
SQL> exec LOCAL_PACK.local_test(1);
BEGIN LOCAL_PACK.local_test(1); END;
*
ERROR at line 1:
ORA-04068: existing state of packages has been discarded
ORA-04062: signature of package "YASBS.TEST_PACK" has been changed
ORA-06512: at "YASBS.LOCAL_PACK", line 4
ORA-06512: at line 1
SQL> select status,object_name,object_type from user_objects where object_name='LOCAL_PACK';
STATUS OBJECT_NAME OBJECT_TYPE
------- ------------------------------ ------------------
VALID LOCAL_PACK PACKAGE
INVALID LOCAL_PACK PACKAGE BODY
SQL> exec LOCAL_PACK.local_test(1);
PL/SQL procedure successfully completed.
SQL> select status,object_name,object_type from user_objects where object_name='LOCAL_PACK';
STATUS OBJECT_NAME OBJECT_TYPE
------- ------------------------------ ------------------
VALID LOCAL_PACK PACKAGE
VALID LOCAL_PACK PACKAGE BODY
The second execution compiles the package and returns the status to valid.
How can we know beforehand that the local program will be invalidated on the first execution? The only way I can think of is to check the dependencies across all databases involved. By collecting all rows from dba_dependencies from all databases we can see that when the remote program is changed the programs on other databases that use this remote program will be invalidated when they are executed. Then we can compile these programs and see if they compile without errors.
Database links may be very annoying sometimes, this case is just one of them.
Wednesday, August 06, 2008
Index block split bug in 9i
In his famous index internals presentation Richard Foote mentions a bug in 9i about index block splits when rows are inserted in the order of the index columns. Depending on when you commit your inserts the index size changes dramatically.
While I was trying to find out why a 3-column primary key index takes more space than its table I recalled that bug and it turned out that was the reason of the space issue. The related bug is 3196414 and it is fixed in 10G.
Here is the test case Richard presents in his paper.
SQL> create table t(id number,value varchar2(10));
Table created.
SQL> create index t_ind on t(id);
Index created.
SQL> @mystat split
NAME VALUE
------------------------------ ----------
leaf node splits 0
leaf node 90-10 splits 0
branch node splits 0
SQL> ed
Wrote file afiedt.buf
1 begin
2 for i in 1..10000 loop
3 insert into t values(i,'test');
4 commit;
5 end loop;
6* end;
SQL> r
1 begin
2 for i in 1..10000 loop
3 insert into t values(i,'test');
4 commit;
5 end loop;
6* end;
PL/SQL procedure successfully completed.
SQL> @mystat2 split
NAME VALUE DIFF
------------------------------ ---------- ----------
leaf node splits 35 35
leaf node 90-10 splits 0 0
branch node splits 0 0
SQL> analyze index t_ind validate structure;
Index analyzed.
SQL> select lf_blks, pct_used from index_stats;
LF_BLKS PCT_USED
---------- ----------
36 51
SQL> drop table t;
Table dropped.
I am trying to insert the rows in the order of the primary key column, so what I expect to see is that when an index block fills there will be a 90-10 split and the index will grow in size. But as the number of leaf block splits show there are 35 block splits and none of them are 90-10 splits meaning all are 50-50 block splits. I have 36 leaf blocks but half of each one is empty.
If we try the same inserts but commit after the loop the result changes.
SQL> create table t(id number,value varchar2(10));
Table created.
SQL> create index t_ind on t(id);
Index created.
SQL> @mystat split
NAME VALUE
------------------------------ ----------
leaf node splits 35
leaf node 90-10 splits 0
branch node splits 0
SQL> ed
Wrote file afiedt.buf
1 begin
2 for i in 1..10000 loop
3 insert into t values(i,'test');
4 end loop;
5 commit;
6* end;
SQL> r
1 begin
2 for i in 1..10000 loop
3 insert into t values(i,'test');
4 end loop;
5 commit;
6* end;
PL/SQL procedure successfully completed.
SQL> @mystat2 split
NAME VALUE DIFF
------------------------------ ---------- ----------
leaf node splits 53 53
leaf node 90-10 splits 18 18
branch node splits 0 0
SQL> analyze index t_ind validate structure;
Index analyzed.
SQL> select lf_blks, pct_used from index_stats;
LF_BLKS PCT_USED
---------- ----------
19 94
In this case we see that there have been 18 block splits and all were 90-10 splits as expected. We have 19 leaf blocks and all are nearly full. Depending on where the commit is we can get an index twice the size it has to be. When I ran the same test in 10G it did not matter where the commit was. I got 19 leaf blocks in both cases.
I did not test if this problem happens when several sessions insert a single row and commit just like in an OLTP system but I think it is likely because we have indexes showing this behavior in OLTP systems.
Friday, August 01, 2008
OTN members, don't change your e-mail account!
I am regular user of OTN and its forums. Last week I was trying to login to OTN from a public computer and I got the "invalid login" error everytime I tried. I was sure I was typing my password correct but I could not get in anyway. So, I tried to get my password reset and sent to my e-mail address. Then I remembered that the e-mail address I used to register for OTN was from my previous employer meaning I did not have access to it anymore. As OTN does not allow changing the registration e-mail address I was stuck. I send a request from OTN to get my password delivered to my current e-mail address. Here is the reply I got:
Resolution: Oracle's membership management system does not currently support
the editing of the email address or username in your membership profile.
(It will support this capability in a future release.)
Please create a new account with the new email address you wish to use. However,
it is possible to change the email at which you receive
Discussion Forum "watch" emails (see "Your Control Panel" when logged in).They tell me to create a new user and forget about my history, watch list, everything. What a user centric approach this is.If you are an OTN member do not lose your password and your e-mail account at the same time, you will not find anybody from OTN who is willing to solve your problem and help you to recover your password.
I am used to bad behavior and unwillingness to solve problems in Metalink, now I get the same behavior in OTN. Whatever, just wanted to let you know about it.
Thursday, April 17, 2008
Materialized view refresh change in 10G and sql tracing
Complete refresh of a single materialized view used to do a truncate and insert on the mview table until 10G. Starting with 10G the refresh does a delete and insert on the mview table. This guarantees that the table is never empty in case of an error, the refresh process became an atomic operation.
There is another difference between 9.2 and 10G in the refresh process, which I have realized when trying to find out why a DDL trigger prevented a refresh operation. In 9.2 the refresh process runs an ALTER SUMMARY statement against the mview while in 10G it does not.
We have a DDL trigger in some of the test environments (all 9.2) for preventing some operations. The trigger checks the type of the DDL and allows or disallows it based on some conditions. After this trigger was put in place some developers started to complain about some periodic mview refresh operations failing a few weeks ago. I knew it was not because of the TRUNCATE because the trigger allowed truncate operations.
So I enabled sql tracing and found out what the refresh process was doing. Here is a simplified test case for it in 10G.
YAS@10G>create table master as select * from all_objects where rownum<=5;
Table created.
YAS@10G>alter table master add primary key (owner,object_name,object_type);
Table altered.
YAS@10G>create materialized view mview as select * from master;
Materialized view created.
YAS@10G>exec dbms_mview.refresh('MVIEW');
PL/SQL procedure successfully completed.
YAS@10G>create or replace trigger ddl_trigger before ddl on schema
2 begin
3 if ora_sysevent<>'TRUNCATE' then
4 raise_application_error(-20001,'DDL NOT ALLOWED');
5 end if;
6 end;
7 /
Trigger created.
YAS@10G>exec dbms_mview.refresh('MVIEW');
PL/SQL procedure successfully completed.
The refresh was successful in 10G even after the DDL trigger was active. In 9.2 it errors out after the DDL trigger is enabled.
SQL> exec dbms_mview.refresh('MVIEW');
BEGIN dbms_mview.refresh('MVIEW'); END;
*
ERROR at line 1:
ORA-04045: errors during recompilation/revalidation of YAS.MVIEW
ORA-20001: DDL NOT ALLOWED
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 820
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 877
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 858
ORA-06512: at line 1
After enabling sql trace and running the refresh again, the trace file shows the problem statement.
SQL> alter session set sql_trace=true;
Session altered.
SQL> exec dbms_mview.refresh('MVIEW');
BEGIN dbms_mview.refresh('MVIEW'); END;
*
ERROR at line 1:
ORA-04045: errors during recompilation/revalidation of YAS.MVIEW
ORA-20001: DDL NOT ALLOWED
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 820
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 877
ORA-06512: at "SYS.DBMS_SNAPSHOT", line 858
ORA-06512: at line 1
The last statement in the trace file is this:
ALTER SUMMARY "YAS"."MVIEW" COMPILE
So, in 9.2 refresh process runs an ALTER SUMMARY command against the mview. After changing the trigger to allow DDL operations on SUMMARY objects I could refresh the mview without errors.
Tonguc Yilmaz had a recent post about using 10046 for purposes other than performance tuning, like finding out what statements a procedure runs. I find uses for sql tracing nearly everyday and the above case is one of them. When you are not able to understand why an error happens, it is sometimes very useful to turn on sql tracing and examine the trace file. Errors related to specific bind values, errors raised from a "when others" block (you know we do not like "when others", right?) are a couple of things you can dig and analyze with sql tracing.
SQL> r
1 create or replace trigger ddl_trigger before ddl on schema
2 begin
3 if ora_sysevent<>'TRUNCATE' and ora_dict_obj_type<>'SUMMARY' then
4 raise_application_error(-20001,'DDL NOT ALLOWED');
5 end if;
6* end;
Trigger created.
SQL> exec dbms_mview.refresh('MVIEW');
PL/SQL procedure successfully completed.
