oracle technology lovers blog: View Free space from temporary tablespace

oracle technology lovers blog: View Free space from temporary tablespace: select substr(a.tablespace_name,1,20) "TS_name", substr(a.file_name,1,35) "File_Name", round(sum(a.bytes)/1024/1024,2) "Size_MB",sum(NVL(b.b...

oracle technology lovers blog: OS Watcher (OSW

oracle technology lovers blog: OS Watcher (OSW: OS Watcher (OSW) is a collection of UNIX shell scripts intended to collect and archive operating system and network metrics to aid support...

oracle technology lovers blog: Monitor user session.

oracle technology lovers blog: Monitor user session.: set linesize 220 col first_load_time format a20 col client_info format a20 col username format a20 col last_load_time format a20 col sq...

oracle technology lovers blog: How can the ASM instance start when the spfile is ...

oracle technology lovers blog: How can the ASM instance start when the spfile is ...: SQL> show parameter pfile NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ spfile ...

oracle technology lovers blog: Oracle RAC: restoring lost OCR file

oracle technology lovers blog: Oracle RAC: restoring lost OCR file: Shutdown everything oracle instances then run - rootdelete.sh - root.sh this will create OCR Add resource manually.

oracle technology lovers blog: steps to reset original password

oracle technology lovers blog: steps to reset original password: Use below steps to reset original password: Look at the example: schema name is : OASTOLTP SQL> set lines 9999 set pages 9999 set long 90...

oracle technology lovers blog: Extra Redo generation during online backup

oracle technology lovers blog: Extra Redo generation during online backup: There is not excessive redo generated, there is additional information logged into the online redo log during a hot backup the first ti...

oracle technology lovers blog: Oracle RAC Basics

oracle technology lovers blog: Oracle RAC Basics: Oracle RAC is nothing but multiple nodes (each with an Oracle instance) access a same shared database.   ...

oracle technology lovers blog: Difference between Oracle Single instance and Orac...

oracle technology lovers blog: Difference between Oracle Single instance and Orac...: Single  Instance Oracle RAC Single instance accessing database Multiple instances accessing same database Database can be local or shar...

Difference between Oracle Single instance and Oracle RAC

Single  Instance	Oracle RAC
Single instance accessing database	Multiple instances accessing same database
Database can be local or shared	Database must be on shared.
Minimum one node is Required	Minimum two node required
Clusterware software is not required	Clusterware Software is required.
Consists of one SGA and one set of background  processes	Each instance having own  one SGA and one set of background  processes
One set of redo logs	Multiple set redo logs depending on number of instances
No Cache fusion used un Single instance	Cache fusion is used to transfer or access block from remote instance
V$ views to monitor and manage instance	For monitoring at the cluster level Oracle provides GV$ views.
Meeting some of the business requirements (availability, scalability) is limited to a single instance configuration.	Modern business requirements of high availability and linear scalability are provided by multiple instances sharing a common physical database

Oracle RAC Basics

Oracle RAC is nothing but multiple nodes (each with an Oracle instance) access a same shared database.


 

  


Component of Oracle RAC

• Node
• Instance
• Database
• Clusterware software.
• Interconnect
• OCR and Vote disk

Node: Node is individual machine which has operating system install on it.

Instance: Instance is a way to access the database. It is combination of memory and background processes

Database: Database is set of Oracle files such as data file, Control files, Oracle redo log file and Archive log file

Clusterware software: It maintains integrity of Oracle database and manages shared and local resources.

Interconnect: Interconnect is nothing but network link between nodes. It maintains network heartbeat between RAC nodes. It also useful send block to other instance through network in case of cache fusion.

OCR: The OCR maintains cluster configuration information that is used by each node of the cluster to determine the state of the cluster. The OCR also maintains information on application resources that are defined within Clusterware such as databases, instance, services and the like and is therefore constantly changing. Each node in the cluster maintains a copy of the OCR in memory for better performance and each node is responsible for updating the OCR as required.

Vote Disk:The Voting Disk Files are used by Oracle Clusterware to determine which nodes are currently members of the cluster. The voting disk files are also used in concert with other Cluster components such as CRS to maintain the clusters integrity. As with most everything else Clusterware/RAC related, you need to consider redundancy in your architecture. Oracle expects that you will configure at least 3 voting disks for redundancy purposes. You should always configure an odd number of voting disks >= 3. This is because loss of more than half your voting disks will cause the entire cluster to fail.

Useful links

HOWTO: Manually Convert Single Instance to RAC on Unix
http://orabackus.wordpress.com/2007/11/18/howto-manually-convert-single-instance-to-rac-on-unix/

ASMLib

https://blogs.oracle.com/wim/entry/asmlib

Oracle Clusterware Node Fencing
http://www.trivadis.com/uploads/tx_cabagdownloadarea/Trivadis_oracle_clusterware_node_fencing_v.pdf

Oracle Database 12c: New Features - Pluggable Databases

http://www.orafaq.com/node/2756

ASM: Difference's between CORSE and FINE Striping

COARSE STRIPING	FINE GRAINED STRIPING
It is used for all voluminous input/output, e.g. input/output operations on datafiles.	It is used for all small input/output, e.g. input/output operations on online redolog files and control files.
The size of the coarse grained data stripes is large.	The size of the fine grained data stripes is small.
It manages the load balance across the disk groups.	It spreads the load on disk groups reducing latency for certain file types.
The size of the coarse-grained stripe is always equal to the size of ASM Allocation Units (AU).	The size of the fine-grained stripe is always 128 KB.
The size for coarse striping can be set using the _asm_ausize parameter.	The size for fine grained striping can be set using the _asm_stripesize parameter.

Extra Redo generation during online backup

There is not excessive redo generated, there is additional information logged into the online redo log during a hot backup the first time a block is modified in a tablespace that is in hot backup mode. In hot backup mode only 2 things are different:

The first time a block is changed in a datafile that is in hot backup mode, the ENTIRE 

BLOCK is written to the redo log files, not just the changed bytes.  Normally only the 

changed bytes (a redo vector) is written. In hot backup mode, the entire block is logged 

the FIRST TIME.  This is because you can get into a situation where the process copying 

the datafile and DBWR are working on the same block simultaneously.  Lets say they are 

and the OS blocking read factor is 512bytes (the OS reads 512 bytes from disk at a time). 

 The backup program goes to read an 8k Oracle block.  The OS gives it 4k.  Meanwhile -- 

DBWR has asked to rewrite this block.  the OS schedules the DBWR write to occur right 

now.  The entire 8k block is rewritten.  The backup program starts running again 

(multi-tasking OS here) and reads the last 4k of the block.  The backup program has now 

gotten an impossible block -- the head and tail are from two points in time.  We cannot 

deal with that during recovery.  Hence, we log the entire block image so that during 

recovery, this block is totally rewritten from redo and is consistent with itself at 

least.  We can recover it from there.

The datafile headers which contain the SCN of the last completed checkpoint are NOT
updated while a file is in hot backup mode.  This lets the recovery process understand
what archive redo log files might be needed to fully recover this file.

To limit the effect of this additional logging, you should ensure you only place one
tablepspace at a time in backup mode and bring the tablespace out of backup mode as soon
as you have backed it up.  This will reduce the number of blocks that may have to be
logged to the minimum possible.

steps to reset original password

Use below steps to reset original password:

Look at the example:

schema name is : OASTOLTP

SQL> set lines 9999
set pages 9999
set long 90000000SQL> SQL>
SQL>
SQL> select dbms_metadata.get_ddl('USER','OASTOLTP') from dual;

DBMS_METADATA.GET_DDL('USER','OASTOLTP')
--------------------------------------------------------------------------------

CREATE USER "OASTOLTP" IDENTIFIED BY VALUES 'S:46DE8181197D5D6A2BEE2B43B21762
BE9B725B07217DA76100F37D12598D;6B9A3DF7BDFDD198'
DEFAULT TABLESPACE "USERS"
TEMPORARY TABLESPACE "TEMP_0"


SQL>

to reset original password you will user above command as

ALTER USER OASTOLTP IDENTIFIED BY 'you will get encrypted password of OASTOLTP' default tablespace ........