Understanding RMAN

-


Rman Backups:
============

SYSBACKUP PRIVILEGE : Introduced in oracle 12c database
===================
• New system privileges introduced is SYSBACKUP
• Granted to users who need to perform backup and recovery operations.
• A user with the SYSBACKUP privilege will be restricted to allow only backup and recovery operations.
• This permission can also be granted to a local user account in a PDB

eg:

RMAN> connect target /
connected to target database: CDBTST (DBID=1036753271)
RMAN> connect target '"xyz  as sysbackup"';
target database Password:
connected to target database: CDBTST (DBID=1036753271)


RMAN:
====

a RMAN (Recovery Manager)

 RMAN is a centralised backup restore and recovery utility across the enterprise database;
 If we configure RMAN there will be minimal DBA intervention during restore and recovery
 We can configure RMAN in CATALOG mode and NO CATALOG mode
 Oracle stringly recomends to configure RMAN in catalog mode
 In No catalog mode information about the configuration parameters and backup sets will be stored in the reusable section of the target database control file
 we can save the backup information using the control_file_record_keep_time
 Invocation of every RMAN backup command produces backup sets which are nothing but collection of backup pieces which are nothing but physical files
 We can take full/differential/incremental using RMAN
In case of incremental backups RMAN takes the backup of only modified blocks
RMAN backup is a content copy
In order to minimize the backup time we can define multiple channels
A channel is a communication path from catalog database to target database
No of channel depends on number of CPUS
If a server is a uni processor and we have defined channels of 3 then there will be no use
we can clone the database using duplicate database
we can create stand by database using RMAN
To minimize the incremental backup time oracle has introduced block chnage tacking
Once we enable BCT then it will initiate CTWR(change Track writer)
Using RMAN we can take compressed backups
Using catalog database we can retain the information about the backups until we donot delet explicitly
In catalog database we can create stored scripts and the scripts can be reused for any number of target databases


Steps to configure CATALOG database:
====================================
Identify a least utilised server running on any paltform
create a suitable database for catalog
create a seperate tablespace to hold the rman database
create a seperate user and grant connect,resource,recovery_catalog_owner
connect to RMAN utility and execute "create catalog"
Now execute register database


Working on RMAN configuration:
===========================
RMAN on its own capable of taking the backups in to disk based on archive dest value
But it cannot directly push the backup pieces to the tape until the intervention of third party MML layer like TIVOLI?VERITAS/LEGATO/OSB
From 10g oracle introduced OSB(oracle secure backup ) to minimise tyhe MML intervention to tape libraris
Incase of TIVOLI TSM administrator is going to install teh TSM software and its going to configure TDPO.opt file on all the target database TDPO
Once the tdpo agenr is installed and configured on the target databases it is the responsibility of the dba to modify the RMAN scripts to point to the TDPO.opt file location

CONFIGURE  RETENTION POLICY TO REDUNDANCY 2
This above parameter explain us that it will maintain 2 copies of backup pieces, but this is not a good practice to use
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW OF 31 DAYS
CONFIGURE BACKUP OPTIMIZATION ON
CONFIGURE DEFAULT DEVICE TO DISK
CONFIGURE CONTROLFILE AUTOBACKUP ON
CONFIGURE DEVICE TYPE DISK PARALLELISM


RMAN  COMMANDS:
==============

RMAN > LIST BACKUP;
RMAN > SHOW ALL;
RMAN > REPORT NEED BACKUP; Using the report command,we can get information about RMAN backups which correspond to current retention policy.
RMAN > BACKUP DATABASE;
RMAN > REPORT SCHEMA;// To get information about datafiles of a database according to a specific point in time, use the following:
report schema at time sysdate-1';
report schema at scn=554962;
report schema at sequence 3 thread 1;



RMAN SCRIPT:
==========

run
{
allocate channel t1 device type disk;
allocate channel t2 device type disk;
allocate channel t3 device type disk;
allocate channel t4 device type disk;
backup archivelog all delete all input //In this case RMAN backs up only one copy of each log sequence number in these directories, and then deletes all copies of any log that it backed up from the archiving destinations.
sql 'alter system switch logfile';
release channel t1;
release channel t2;
release channel t3;
release channel t4;
}


Useful commands
===============
backup database plus archivelog all delete all input;
crosscheck archivelog all;
backup incremental level 0 database;
backup incremental level 1 database;
backup as compressed backupset database;
crosscheck backup
delete obsolete


Backup strategy


Types of Incremental  backup

1) Cumulative
   - Which includes all block changes since the most recent level 0 backup 
2) Differential
   - Which includes only blocks changed since the most recent incremental backup. Incremental backups are differential by default.

 
   Making Incremental Backup


    - It captures the block level changes to the database after incremental or full backups
    - By generally incremental is smaller and faster than full backup and  Recovery with incremental backups is faster than using redo logs alone.
    - In this incremental backup starting is “Level 0” Which is same as a full backup  but it ll  set  a backup strategy.
    - In “Level 1” backup  which contains only blocks changed after a previous incremental backup , if  our  current database or parent database incarnation doesn’t have the “Level 0” backup we would directly proceed for “Level 1” then it ll take automatically “Level 0”



Typical Backup Options

1)Format  => Backup format  ‘%U_%d_%t_%s_%p’
              Here %U=Unique name ,%d=database name,%t=backup set time stamp,%s=backup set number,%p=backup piece number
 2)TAG => BACKUP TAG 'weekly_full_db_bkup'  DATABASE MAXSETSIZE 10M;
             We are allocating the name of rman Backup   if we don't mention the tag by default the rman allocates the name using date and time


We can implement three kinds of backup strategies
1) Level 0 or full backup - Monthly once
2) Level 1 Cumulative -  Weekly Once
3) Level 1 Differential -  Daily  Once

RMAN> backup format 'Dh_%U_%d_%t_%s_%p'Tag 'Incre_backup_1' incremental level 1 database;
RMAN > backup  format 'Dh_%U_%d_%t_%s_%p' Tag 'Incre_culMul' incremental level 1 cumulative database;

Note: if we are going to take level  0 or Full backup a thumb rule is to take a new backup when the data of 50% has been changed. We can observe also by using this query



SQL> SELECT FILE#, INCREMENTAL_LEVEL, COMPLETION_TIME, BLOCKS, DATAFILE_BLOCKS FROM V$BACKUP_DATAFILE WHERE INCREMENTAL_LEVEL > 0 AND BLOCKS / DATAFILE_BLOCKS > .5 ORDER BY COMPLETION_TIME;



FUll DB crash:
=============
RMAN > backup database;
RMAN > sql ' alter system switch logfile';


Now remove CRD files

RMAN > shut abort
RMAN > startup nomount;
RMAN > restore controlfile;
RMAN> sql 'alter database mount';
RMAN > restore database;
RMAN> recover database;
RMAN > sql ' alter database open resetlogs';
RMAn > list incarnation;




Comments

Post a Comment

Popular posts from this blog

Understanding Terraform

-
 Terraform is a tool used  for building, changing, and versioning infrastructure safely and efficiently. A Terraform can manage multiple cloud services using a provider plugin  Terraform work flow? Terraform work flow will be comprised of validate -> plan -> apply and finally destroy. what is the important file of terraform which records the actions of Terraform apply? For every Terraform execution the action will be recorded in a file called Terraform state file .  The terraform init command is used to initialise a working directory containing Terraform configuration files. During init, the configuration is searched for module blocks, and the source code for referenced modules is retrieved from the locations given in  their source arguments. The terraform plan command is used to create an execution plan. It will not modify things in infrastructure. The terraform apply command is used to apply the changes required to reach the desired state of the configur...
Read more

How to make CRS and ASM not to restart after server reboot

-
I have noticed that server rebooting is taking lot of time on a VM machine for every reboot, so I have decided to auto start of the crs and ASM service During this phase I have noticed an attribute called auto_start when I try to execute the below command crsctl stat res -p This AUTO_START attribute is there for several resources like ora.ASM ,ora.crs,ora.DATA_DG it has got 2 options restore(0) , never(2) and always (1) always (1)  Causes the resource to restart when the node restarts regardless of the resource’s state when the node stopped -restore (0)  Does not start the resource at restart time if it was in an offline state, such as STATE=OFFLINE, TARGET=OFFLINE, when the node stopped. The resource is restored to its state when the node went down. The resource is started only if it was online before and not otherwise. -never (2)  Oracle Clusterware never restarts the resource regardless of the resource’s state when the node is stopped. So I have dec...
Read more

How to repair ASM disk header

-
Image
What is ASM disk header corruption? ASM disk header corruption is a loss or damage to the disk header which contains the metadata essential for the operation and availability of an ASM disk group in Oracle. Imagine that you have an ASM disk corruption in any of the ASM diskgroups that have critical business data and the diskgroup has been configured as "EXTERNAL" redundancy, meaning that if one disk is inaccessible the whole diskgroup will be unavailable. Now what? Is your only option to restore it from backup by recreating the diskgroup or are there any other faster ways to recover the data? Here you need to find out whether it’s a complete loss of data in the ASM disk or is it just a header corruption. Hopefully for you, this is just a header corruption. Because, yes, there is a way out!  Below find the steps to restore from the ASM header corruption. Most of the data in the ASM disk header is of interest to that disk only. However, some information in the ASM disk header ...
Read more