Oracle 10G New Feature........Part 1

Question

Dear all,
from last couple of days i was very busy with my oracle 10g box,so i think this is right time to
share some intresting feature on 10g and some internal stuff with all of you.
Have a look :-
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Oracle 10g Memory and Storage Feature.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
1.Automatic Memory Management.
2.Online Segment Shrink
3.Redolog Advisor, checkpointing
4.Multiple Temporary tablespace.
5.Automatic Workload Repository
6.Active Session History
7.Misc
a)Rename Tablespace
b)Bigfile tablespace
c)flushing buffer cache
8.ORACLE INTERNAL
a)undocumented parameter (_log_blocks_during_backup)
b)X$ view (x$messages view)
c)Internal Structure of Controlfile
1.Automatic memory management
================================
This feature reduce the overhead of oracle DBA.previously mostly time we need to set diff oracle SGA parameter for
better performance with the help of own experience,advice views and by monitoring the behaviour
of oracle database.
this was just time consuming activity.........
Now this feature makes easy life for oracle DBA.
Just set SGA_TARGET parameter and it automatically allocate memory to different SGA parameter.
it focus on DB_CACHE_SIZE
SHARED_POOL_SIZE
LARGE_POOL
JAVA_POOL
and automatically set it as
__db_cache_size
__shared_pool_size
__large_pool_size
__java_pool_size
check it in alert_log
MMAN(memory manager) process is new in 10g and this is responsible for sga tuning task.
it automatically increase and decrease the SGA parameters value as per the requirement.
Benefit:- Maximum utlization of available SGA memory.
2.Online Segment Shrink.
==========================
hmmmmm again a new feature by oracle to reduce the downtime.Now oracle mainly focus on availablity
thats why its always try to reduce the downtime by intrducing new feature.
in previous version ,reducing High water mark of table was possible by
Exp/imp
or
alter table move....cmd. but on these method tables was not available for normal use for long hrs if it has more data.
but in 10g with just few command we can reduce the HWmark of table.
this feature is available for ASSM tablespaces.
1.alter table emp enable row movement.
2.alter table emp shrink space.
the second cmd have two phases
first phase is to compact the segment and in this phase DML operations are allowed.
second phase(shrink phase)oracle shrink the HWM of table, DML operation will be blocked at that time for short duration.
So if want to shrink the HWM of table then we should use it with two diff command
first compact the segment and then shrink it on non-peak hrs.
alter table emp shrink space compact. (This cmd doesn't block the DML operation.)
and alter table emp shrink space. (This cmd should be on non-peak hrs.)
Benefit:- better full table scan.
3.Redolog Advisor and checkpointing
================================================================
now oracle will suggest the size of redo log file by V$INSTANCE_RECOVERY
SELECT OPTIMAL_LOGFILE_SIZE
FROM V$INSTANCE_RECOVERY
this value is influence with the value of FAST_START_MTTR_TARGET .
Checkpointing
Automatic checkpointing will be enable after setting FAST_START_MTTR_TARGET to non-zero value.
4.Multiple Temporary tablespace.
==================================
Now we can manage multiple temp tablespace under one group.
we can create a tablespace group implicitly when we include the TABLESPACE GROUP clause in the CREATE TEMPORARY TABLESPACE or ALTER TABLESPACE statement and the specified tablespace group does not currently exist.
For example, if group1 is not exists,then the following statements create this groups with new tablespace
CREATE TEMPORARY TABLESPACE temp1 TEMPFILE '/u02/oracle/data/temp01.dbf'
SIZE 50M
TABLESPACE GROUP group1;
--Add Existing temp tablespace into group by
alter tablespace temp2 tablespace group group1.
--we can also assign the temp tablespace group on database level as default temp tablespace.
ALTER DATABASE <db name> DEFAULT TEMPORARY TABLESPACE group1;
benefit:- Better I/O
One sql can use more then one temp tablespace
5.AWR(Automatic Workload Repository):-
================================== AWR is built in Repository and Central point of Oracle 10g.Oracle self managing activities
is fully dependent on AWR.by default after 1 hr, oracle capure all database uses information and store in AWR with the help of
MMON process.we called it Memory monitor process.and all these information are kept upto 7 days(default) and after that it automatically purge.
we can generate a AWR report by
SQL> @?/rdbms/admin/awrrpt
Just like statspack report but its a advance and diff version of statspack,it provide more information of Database as well as OS.
it show report in Html and Text format.
we can also take manually snapshot for AWR by
BEGIN
DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT ();
END;
**The STATISTICS_LEVEL initialization parameter must be set to the TYPICAL or ALL to enable the Automatic Workload Repository.
[oracle@RMSORA1 oracle]$ sqlplus / as sysdba
SQL*Plus: Release 10.1.0.2.0 - Production on Fri Mar 17 10:37:22 2006
Copyright (c) 1982, 2004, Oracle. All rights reserved.
Connected to:
Oracle Database 10g Enterprise Edition Release 10.1.0.2.0 - Production
With the Partitioning, OLAP and Data Mining options
SQL> @?/rdbms/admin/awrrpt
Current Instance
~~~~~~~~~~~~~~~~
DB Id DB Name Inst Num Instance
4174002554 RMSORA 1 rmsora
Specify the Report Type
~~~~~~~~~~~~~~~~~~~~~~~
Would you like an HTML report, or a plain text report?
Enter 'html' for an HTML report, or 'text' for plain text
Defaults to 'html'
Enter value for report_type: text
Type Specified: text
Instances in this Workload Repository schema
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
DB Id Inst Num DB Name Instance Host
* 4174002554 1 RMSORA rmsora RMSORA1
Using 4174002554 for database Id
Using 1 for instance number
Specify the number of days of snapshots to choose from
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Entering the number of days (n) will result in the most recent
(n) days of snapshots being listed. Pressing <return> without
specifying a number lists all completed snapshots.
Listing the last 3 days of Completed Snapshots
Snap
Instance DB Name Snap Id Snap Started Level
rmsora RMSORA 16186 16 Mar 2006 17:33 1
16187 16 Mar 2006 18:00 1
16206 17 Mar 2006 03:30 1
16207 17 Mar 2006 04:00 1
16208 17 Mar 2006 04:30 1
16209 17 Mar 2006 05:00 1
16210 17 Mar 2006 05:31 1
16211 17 Mar 2006 06:00 1
16212 17 Mar 2006 06:30 1
16213 17 Mar 2006 07:00 1
16214 17 Mar 2006 07:30 1
16215 17 Mar 2006 08:01 1
16216 17 Mar 2006 08:30 1
16217 17 Mar 2006 09:00 1
Specify the Begin and End Snapshot Ids
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Enter value for begin_snap: 16216
Begin Snapshot Id specified: 16216
Enter value for end_snap: 16217
End Snapshot Id specified: 16217
Specify the Report Name
~~~~~~~~~~~~~~~~~~~~~~~
The default report file name is awrrpt_1_16216_16217.txt. To use this name,
press <return> to continue, otherwise enter an alternative.
Benefit:- Now DBA have more free time to play games.....................:-)
Advance version of statspack
more DB and OS information with self managing capabilty
New Automatic alert and database advisor with the help of AWR.
6.Active Session History:-
==========================
V$active_session_history is view that contain the recent session history.
the memory for ASH is comes from SGA and it can't more then 5% of Shared pool.
So we can get latest and active session report from v$active_session_history view and also get histortical data of
of session from DBA_HIST_ACTIVE_SESS_HISTORY.
v$active_session_history include some imp column like:-
~SQL identifier of SQL statement
~Object number, file number, and block number
~Wait event identifier and parameters
~Session identifier and session serial number
~Module and action name
~Client identifier of the session
7.Misc:-
========
Rename Tablespace:-
=================
in 10g,we can even rename a tablespace by
alter tablespace <tb_name> rename to <tb_name_new>;
This command will update the controlfile,data dictionary and datafile header,but dbf filename will be same.
**we can't rename system and sysaux tablespace.
Bigfile tablespace:-
====================
Bigfile tablespace contain only one datafile.
A bigfile tablespace with 8K blocks can contain a 32 terabyte datafile.
Bigfile tablespaces are supported only for locally managed tablespaces with automatic segment-space management.
we can take the advantage of bigfile tablespace when we are using ASM or other logical volume with RAID.
without ASM or RAID ,it gives poor response.
syntax:-
CREATE BIGFILE TABLESPACE bigtbs
Flushing Buffer Cache:-
======================
This option is same as flushing the shared pool,but only available with 10g.
but i don't know, whats the use of this command in prod database......
anyway we can check and try it on test server for tuning n testing some query etc....
SQL> alter system flush buffer_cache;
System altered.
++++++++++++++++++
8.Oracle Internal
++++++++++++++++++
Here is some stuff that is not related with 10g but have some intresting things.
a)undocumented parameter "_log_blocks_during_backup"
++++++++++++++++++++++++
as we know that oracle has generate more redo logs during hotbackup mode because
oracle has to maintain the a complete copy of block into redolog due to split block.
we can also change this behaviour by setting this parameter to False.
If Oracle block size equals the operating system block size.thus reducing the amount of redo generated
during a hot backup.
WITHOUT ORACLE SUPPORT DON'T SET IT ON PROD DATABASE.THIS DOCUMENT IS JUST FOR INFORMATIONAL PURPOSE.
b)some X$ views (X$messages)
++++++++++++++++
if you are intresting in oracle internal architecture then x$ view is right place for getting some intresting things.
X$messages :-it show all the actions that a background process do.
select * from x$messages;
like:-
lock memory at startup MMAN
Memory Management MMAN
Handle sga_target resize MMAN
Reset advisory pool when advisory turned ON MMAN
Complete deferred initialization of components MMAN
lock memory timeout action MMAN
tune undo retention MMNL
MMNL Periodic MQL Selector MMNL
ASH Sampler (KEWA) MMNL
MMON SWRF Raw Metrics Capture MMNL
reload failed KSPD callbacks MMON
SGA memory tuning MMON
background recovery area alert action MMON
Flashback Marker MMON
tablespace alert monitor MMON
Open/close flashback thread RVWR
RVWR IO's RVWR
kfcl instance recovery SMON
c)Internal Structure of Controlfile
++++++++++++++++++++++++++++++++++++
The contents of the current controlfile can be dumped in text form.
Dump Level Dump Contains
1 only the file header
2 just the file header, the database info record, and checkpoint progress records
3 all record types, but just the earliest and latest records for circular reuse record types
4 as above, but includes the 4 most recent records for circular reuse record types
5+ as above, but the number of circular reuse records included doubles with each level
the session must be connected AS SYSDBA
alter session set events 'immediate trace name controlf level 5';
This dump show lots of intresting information.
it also show rman recordes if we used this controlfile in rman backup.
Thanks
Kuljeet Pal Singh

Answer 1

You can find each doc in html and pdf format on the Documentation Library<br>
You can too download all the documentation in html format to have all on your own computer here (445.8MB)<br>
<br>
Nicolas.