UKoom » Oracle

Register table issue caused by using wrong column type in SQL

ukoom — Tue, 07 Dec 2010 03:54:26 +0000

Wow, how long the title is!

I came across one strange issue today (actually I found this last Friday, but you know weekend coming, hehehe).

When using the update DQL to fill up one new column in the registered table, there are always lots of blanks appended.

The root cause after doing some investigation, what I found:

We are adding the column in type – char rather than varchar2 which is the normal one.

CHAR should be used for storing fix length character strings. String values will be space/blank padded before stored on disk.

Baiqing, one of my colleges , wrote the DQL to add the new column. I believe that:

1. He should be more careful

2. The DQL used to register table in Documentum are defining the type as ‘char’. Documentum is using ‘char’ type to define variable length character strings. there is no type to define fix length strings. That make developer confused.

Anyway, the cause was found. Happy Monday!!!!

Reference:

http://www.orafaq.com/faq/what_is_the_difference_between_varchar_varchar2_and_char_data_types

Get definition for view in Oracle

ukoom — Fri, 23 Apr 2010 01:19:36 +0000

set LONG 10000
select TEXT from ALL_VIEWS where view_name = ‘MY_VIEW‘;

Line one must be at least the size of the statement used to create the view. Either pick a really big number if you think the view is large or use the following to determine how long it is first. If it isn’t, the text will be truncated

select text_length from all_views where view_name = ‘MY_VIEW’

NOTE: name of the view is case sensitive as are most every thing in Oracle.

If you want to capture output to something other than a SQL Plus window such as a file, be sure to include do the following before you execute the select statement.

spool c:\v_person.sql

To close the file when you are done writing output to it, call the following:

spool off

To summarize:

select text_length from all_views where view_name = ‘MY_VIEW’

10000

– whatever value you get back, use on the next statement.

set LONG 10000

spool c:\v_person.sql

select TEXT from ALL_VIEWS where view_name = ‘MY_VIEW‘;

spool off

Oracle Tuning Documentum Server

ukoom — Mon, 07 Dec 2009 06:44:56 +0000

Modifying the dmcl.ini File on the Oracle WebCenter Content Service for Documentum Host

On all computers that host the Oracle WebCenter Content Service for Documentum, you can increase the max_session_count variable in the dmcl.ini file to allow for additional concurrent sessions. By default, the max_session_count is set to 10, meaning there can be 10 concurrent sessions to Documentum.

The number of Documentum sessions depends on the number of content crawlers you expect to run concurrently, as well as the number of users you expect to click through links concurrently. We recommend you set the max_session_count parameter accordingly. You can increase this setting later if you find that you run out of sessions or want to increase the number of content crawlers running simultaneously.
A session is started for each user with a unique user name/password that tries to click through to a Documentum document in the portal. The max_session_count must accommodate the estimated number of click through users to be handled concurrently.

Modifying the server.ini File on the Documentum Server

On the Documentum Server computer, you can change the settings in the server.ini file to allow for additional concurrent sessions.

The concurrent_sessions variable controls the number of connections the Documentum server can handle concurrently. This parameter should accommodate for the sum of all the max_session_count values in your environment.

If you plan to use the Oracle WebCenter Content Service for Documentum with several different docbases, you must modify the server.ini for each docbase. When making these configuration changes, consider the following:

As with any configuration changes, take into account any hardware limitations.
The configuration settings depend on both existing and projected Documentum usage.

Oracle Session Statistics

ukoom — Mon, 07 Dec 2009 05:55:32 +0000

Here are some scripts related to Session Statistics .

Session I/O By User

SESSION I/O BY USER NOTES:

Username – Name of the Oracle process user

OS User – Name of the operating system user

PID – Process ID of the session

SID – Session ID of the session

Serial# – Serial# of the session

Physical Reads – Physical reads for the session

Block Gets – Block gets for the session

Consistent Gets – Consistent gets for the session

Block Changes – Block changes for the session

Consistent Changes – Consistent changes for the session

select	nvl(ses.USERNAME,'ORACLE PROC') username,
	OSUSER os_user,
	PROCESS pid,
	ses.SID sid,
	SERIAL#,
	PHYSICAL_READS,
	BLOCK_GETS,
	CONSISTENT_GETS,
	BLOCK_CHANGES,
	CONSISTENT_CHANGES
from	v$session ses,
	v$sess_io sio
where 	ses.SID = sio.SID
order 	by PHYSICAL_READS, ses.USERNAME

CPU Usage By Session

CPU USAGE BY SESSION NOTES:

Username – Name of the user

SID – Session id

CPU Usage – CPU centiseconds used by this session (divide by 100 to get real CPU seconds)

select 	nvl(ss.USERNAME,'ORACLE PROC') username,
	se.SID,
	VALUE cpu_usage
from 	v$session ss,
	v$sesstat se,
	v$statname sn
where  	se.STATISTIC# = sn.STATISTIC#
and  	NAME like '%CPU used by this session%'
and  	se.SID = ss.SID
order  	by VALUE desc

Resource Usage By User

RESOURCE USAGE BY USER NOTES:

SID – Session ID

Username – Name of the user

Statistic – Name of the statistic

Value – Current value

select 	ses.SID,
	nvl(ses.USERNAME,'ORACLE PROC') username,
	sn.NAME statistic,
	sest.VALUE
from 	v$session ses,
	v$statname sn,
	v$sesstat sest
where 	ses.SID = sest.SID
and 	sn.STATISTIC# = sest.STATISTIC#
and 	sest.VALUE is not null
and 	sest.VALUE != 0
order 	by ses.USERNAME, ses.SID, sn.NAME

Session Stats By Session

SESSION STAT NOTES:

Username – Name of the user

SID – Session ID

Statistic – Name of the statistic

Usage – Usage according to Oracle

select  nvl(ss.USERNAME,'ORACLE PROC') username,
	se.SID,
	sn.NAME stastic,
	VALUE usage
from 	v$session ss,
	v$sesstat se,
	v$statname sn
where  	se.STATISTIC# = sn.STATISTIC#
and  	se.SID = ss.SID
and	se.VALUE > 0
order  	by sn.NAME, se.SID, se.VALUE desc

Cursor Usage By Session

CURSOR USAGE BY SESSION NOTES:

Username – Name of the user

Recursive Calls – Total number of recursive calls

Opened Cursors – Total number of opened cursors

Current Cursors – Number of cursor currently in use

select 	user_process username,
	"Recursive Calls",
	"Opened Cursors",
	"Current Cursors"
from  (
	select 	nvl(ss.USERNAME,'ORACLE PROC')||'('||se.sid||') ' user_process,
			sum(decode(NAME,'recursive calls',value)) "Recursive Calls",
			sum(decode(NAME,'opened cursors cumulative',value)) "Opened Cursors",
			sum(decode(NAME,'opened cursors current',value)) "Current Cursors"
	from 	v$session ss,
		v$sesstat se,
		v$statname sn
	where 	se.STATISTIC# = sn.STATISTIC#
	and 	(NAME  like '%opened cursors current%'
	or 	 NAME  like '%recursive calls%'
	or 	 NAME  like '%opened cursors cumulative%')
	and 	se.SID = ss.SID
	and 	ss.USERNAME is not null
	group 	by nvl(ss.USERNAME,'ORACLE PROC')||'('||se.SID||') '
)
orasnap_user_cursors
order 	by USER_PROCESS,"Recursive Calls"

User Hit Ratios

USER HIT RATIO NOTES:

Username – Name of the user

Consistent Gets – The number of accesses made to the block buffer to retrieve data in a consistent mode.

DB Blk Gets – The number of blocks accessed via single block gets (i.e. not through the consistent get mechanism).

Physical Reads – The cumulative number of blocks read from disk.

Logical reads are the sum of consistent gets and db block gets.

The db block gets statistic value is incremented when a block is read for update and when segment header blocks are accessed.

Hit ratio should be > 90%

select	USERNAME,
	CONSISTENT_GETS,
        BLOCK_GETS,
        PHYSICAL_READS,
        ((CONSISTENT_GETS+BLOCK_GETS-PHYSICAL_READS) / (CONSISTENT_GETS+BLOCK_GETS)) Ratio
from 	v$session, v$sess_io
where 	v$session.SID = v$sess_io.SID
and 	(CONSISTENT_GETS+BLOCK_GETS) > 0
and 	USERNAME is not null
order	by ((CONSISTENT_GETS+BLOCK_GETS-PHYSICAL_READS) / (CONSISTENT_GETS+BLOCK_GETS))

spool命令和使用select语句批量动态生成sql语句

ukoom — Fri, 27 Nov 2009 07:16:45 +0000

今天一个任务是从两张表中用sql语句导出些数据，并且提交这些数据的插入语句。上网查询后找到个方法，例子如下：
spool c:\data.sql;
select ‘insert into table_name values(”’||field_1||”’,”’||field_2||”’);’from table_name where field_n=some_conditon;
spool off;
从这个方案中引申学到两条：spool命令和使用select语句批量拼装sql语句

spool命令

1 Oracle的spool命令可以用来将数据export出来到文本文件。Oracle的Import/Export命令用于备份和恢复比较有效，但对于一些临时数据量的导出，Export不好用，甚至不可用。在这里，就是spool的发挥之地了。

2Spool一般使用格式为spool [filepath]filename; 其他sql语句；spool off;

要输出的内容都在spool语句中包含；

3 spool还有些其他控制命令：

set pagesize 0               –设置页面大小， 0表示无限制，如果设置为10,则10行数据后出现一空行
set num 18                  –设置数字的长度，如果不够大，则用科学记数法显示
set heading off             –设置不要题头，则不出现select的field list
set feedback off           –设置不需要返回信息，比如” 100 rows selected“
set term off                 –
set trimspool on           –trim

4 如果在sqlplus中直接使用sql语句，则导出的数据文件中会包含spool语句中使用的sql语句，如果不想让生成这些可把要使用的sql语句存在一个文件中再在sqlplus中执行此文件即可。

使用select语句批量拼装sql语句

仿照select ‘insert into table_name values(”’||field_1||”’,”’||field_2||”’);’from table_name where field_n=some_conditon;可联想批量生成其他sql语句，例如drop、update、delete语句。其中||为连接符号，三个单引号最后生成一个单引号。

SSH 处理Oracle Clob

ukoom — Wed, 18 Nov 2009 05:03:38 +0000

SSH 处理Oracle Clob

Uninstall Oracle

ukoom — Tue, 17 Nov 2009 15:24:17 +0000

It sure is easier to remove oracle products than to add them….

The method suggested, using Oracle Universal installer to remove the product, is the safest method, and the only reliable means if you have several different ORACLE-HOMEs on you server.

However, if you want to remove all oracle software from your server, the following method will work:

1. Stop all oracle processes (shutdown, kill or reboot – you are goeng to ditch the installation anyway)

2. Remove the $ORACLE_HOME(s) using rm -rf

3. Check the file /etc/oraInst.loc and remove the oraInventory directory structure.

3. Remove the files that remain scattered around your system:

/etc/oraInst.loc

/etc/oratab

/var/tmp/.oracle (directory)

/usr/local/bin/coraenv

/usr/local/bin/dbhome

/usr/local/bin/oraenv

If you remove these files, you will have a fresh system, in an Oracle point of view.

Oracle Flashback Deleted Table

ukoom — Tue, 17 Nov 2009 15:21:05 +0000

SQL> create table tst (col varchar2(10), row_chng_dt date);

Table created.

SQL> insert into tst values ('Version1', sysdate);

1 row created.

SQL> select * from tst ;

COL        ROW_CHNG
---------- --------
Version1   16:10:03
SQL> drop table tst;

Table dropped.

SQL> select object_name, original_name, type, can_undrop as "UND", can_purge as "PUR", droptime
  2  from recyclebin
SQL> /

OBJECT_NAME                    ORIGINAL_NAME TYPE  UND PUR DROPTIME
------------------------------ ------------- ----- --- -------------------
BIN$HGnc55/7rRPgQPeM/qQoRw==$0 TST           TABLE YES YES 2006-09-01:16:10:12
SQL> flashback table tst to before drop;

Flashback complete.

SQL> select * from tst ;

COL        ROW_CHNG
---------- --------
Version1   16:10:03

SQL> select * from recyclebin ;

no rows selected

Reference:

http://www.orafaq.com/node/968

Oracle EXP/IMP FAQs

ukoom — Tue, 17 Nov 2009 15:17:30 +0000

Can one import tables to a different tablespace?ITPUB个人空间g!] g4`6k;W)a
Oracle offers no parameter to specify a different tablespace to import data into. Objects will be re-created in the tablespace they were originally exported from. One can alter this behaviour by following one of these procedures:

Pre-create the table(s) in the correct tablespace:

Import the dump file using the INDEXFILE= optionITPUB个人空间 qW4{�B)hq5I
Edit the indexfile. Remove remarks and specify the correct tablespaces.
;W1~%xL0f,H0G0Run this indexfile against your database, this will create the required tables in the appropriate tablespaces
^O/w N!A$V0Import the table(s) with the IGNORE=Y option.
8^8eYcT0Change the default tablespace for the user:

Revoke the “UNLIMITED TABLESPACE” privilege from the userITPUB个人空间 oG�J,fM8bou;fV
Revoke the user’s quota from the tablespace from where the object was exported. This forces the import utility to create tables in the user’s default tablespace.ITPUB个人空间’K,CJ u`’G
Make the tablespace to which you want to import the default tablespace for the user
E3Y6TReVd[0Import the table

Does one need to drop/ truncate objects before importing?ITPUB个人空间'CH7j ]4O~%t
Before one import rows into already populated tables, one needs to truncate or drop these tables to get rid of the old data. If not, the new data will be appended to the existing tables. One must always DROP existing Sequences before re-importing. If the sequences are not dropped, they will generate numbers inconsistent with the rest of the database.

Note: It is also advisable to drop indexes before importing to speed up the import process. Indexes can easily be recreated after the data was successfully imported.

Can one import/export between different versions of Oracle?
h2i#ElR*t;R0Different versions of the import utility is upwards compatible. This means that one can take an export file created from an old export version, and import it using a later version of the import utility. This is quite an effective way of upgrading a database from one release of Oracle to the next.

Oracle also ships some previous catexpX.sql scripts that can be executed as user SYS enabling older imp/exp versions to work (for backwards compatibility). For example, one can run $ORACLE_HOME/rdbms/admin/catexp7.sql on an Oracle 8 database to allow the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database.

Can one export to multiple files?/ Can one beat the Unix 2 Gig limit?ITPUB个人空间/F9M1h@0^ h`
From Oracle8i, the export utility supports multiple output files. This feature enables large exports to be divided into files whose sizes will not exceed any operating system limits (FILESIZE= parameter). When importing from multi-file export you must provide the same filenames in the same sequence in the FILE= parameter. Look at this example:

exp SCOTT/TIGER FILE=D:F1.dmp,E:F2.dmp FILESIZE=10m LOG=scott.logITPUB个人空间e-iR$|-v3@*?~9n
Use the following technique if you use an Oracle version prior to 8i:

Create a compressed export on the fly. Depending on the type of data, you probably can export up to 10 gigabytes to a single file. This example uses gzip. It offers the best compression I know of, but you can also substitute it with zip, compress or whatever.

# create a named pipe
SnY[*{.L&h&{'n0mknod exp.pipe pITPUB个人空间6B7NZv/A b)X"C*u
# read the pipe - output to zip file in the background
U^M[M`-{$h0gzip < exp.pipe > scott.exp.gz &
U;vDa3f-b8f|\ i0# feed the pipeITPUB个人空间![vC:R1cD#E!_
exp userid=scott/tiger file=exp.pipe ...[/code]
Au�ji�?/g1Km0Contributed by Jared Still

Import directly from a compressed export:

# create a name pipe
9D4DpnKr(mD0mknod imp_pipe pITPUB个人空间sP`sa$Ny&|
# read the zip file and output to pipeITPUB个人空间xe7{&Dk!j�i2C
gunzip < exp_file.dmp.gz > imp_pipe &ITPUB个人空间/ppJ%bn%s4J
# feed the pipeITPUB个人空间I*FB%FXF7J2[)V
impsystem/pwd@sidfile=imp_pipe log=imp_pipe.log ...ITPUB个人空间3S3N-{R~x
Contributed by Blaise BIBOUE.

How can one improve Import/ Export performance?
Q N/h3rBH!F`J)v|0EXPORT:

Set the BUFFER parameter to a high value (e.g. 2Mb -- entered as an integer "2000000")ITPUB个人空间!n B9zNV
Set the RECORDLENGTH parameter to a high value (e.g. 64Kb -- entered as an integer "64000")ITPUB个人空间,M�OM!vxh_0v
Use DIRECT=yes (direct mode export)
:\;\;GtX&|h {0Stop unnecessary applications to free-up resources for your job.
(_w-Q$]$O$Dl9CL0If you run multiple export sessions, ensure they write to different physical disks.ITPUB个人空间+S5i4C;`_J
DO NOT export to an NFS mounted filesystem. It will take forever.
m6K[5_TB\0IMPORT:

Create an indexfile so that you can create indexes AFTER you have imported data. Do this by setting INDEXFILE to a filename and then import. No data will be imported but a file containing index definitions will be created. You must edit this file afterwards and supply the passwords for the schemas on all CONNECT statements.ITPUB个人空间v6k8o5^YQxS{*p
Place the file to be imported on a separate physical disk from the oracle data filesITPUB个人空间?v(W"ps0ok|
Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) considerably in the init$SID.ora file
/t]3K;_a`TF&m0Set the LOG_BUFFER to a big value and restart oracle.
U&t!ev(a2D&PD0Stop redo log archiving if it is running (ALTER DATABASE NOARCHIVELOG;)ITPUB个人空间0` SP’C u(CJ
Create a BIG tablespace with a BIG rollback segment inside. Set all other rollback segments offline (except the SYSTEM rollback segment of course). The rollback segment must be as big as your biggest table (I think?)
e;t#G�P2G!F`w0Use COMMIT=N in the import parameter file if you can afford itITPUB个人空间K,Pw:lVPP`
Use ANALYZE=N in the import parameter file to avoid time consuming ANALYZE statementsITPUB个人空间v^�_0cY^4Y
Remember to run the indexfile previously created
(J*z[o(g\z0Contributed by Petter Henrik Hansen.

What are the common Import/ Export problems?
TB9t7{“G:PY!cF0ORA-00001: Unique constraint (…) violatedITPUB个人空间nj-{@X k m
You are importing duplicate rows. Use IGNORE=NO to skip tables that already exist (imp will give an error if the object is re-created).ITPUB个人空间3kE.R.Ri-}6r
ORA-01555: Snapshot too old
be”~?-Q Z1a-pa-Sm0Ask your users to STOP working while you are exporting or use parameter CONSISTENT=YES
/_6Q }3Qo0ORA-01562: Failed to extend rollback segmentITPUB个人空间yX’d?4{`
Create bigger rollback segments or set parameter COMMIT=Y while importing
5y”u${/@eBgY!E.bZ0IMP-00015: Statement failed … object already exists…
l!n#s N0Gc0Use the IGNORE=Y import parameter to ignore these errors, but be careful as you might end up with duplicate rows.

Reference:

http://www.orafaq.com/wiki/Import_Export_FAQ

Oracle Recompile Invalid Objects

ukoom — Tue, 17 Nov 2009 15:15:39 +0000

Recompile the invalid objects:

SET NEWPAGE 0

SET SPACE 0

SET LINESIZE 80

SET PAGESIZE 0

SET ECHO OFF

SET FEEDBACK OFF

SET HEADING OFF

SET MARKUP HTML OFF

SET ESCAPE \

SPOOL RECOMPILE.SQL

select ‘ALTER VIEW ‘, object_name, ‘compile \;’ from user_objects where status = ‘INVALID’ and object_type=’VIEW’;

SPOOL OFF

Reference:

http://www.oracle-base.com/articles/misc/RecompilingInvalidSchemaObjects.php