Oracle RMAN backup script

                          Oracle RMAN back up script 

A detailed review 

Recovery Manager (RMAN) is an Oracle utility that can backup, restore and recover backup files.This will install along with oracle DB and communicates database server sessions to communicate each other for backup and restore. Let's look what is the benefits of RMAN than conventional backup mechanism .

Makes recovery time proportional to the amount of data recovered

Make backups proportional to the size of transitional changes, not to the size of the database.

Manage the complexity of backup and restore mechanism .

Minimize the possibility of human errors .

Make backups scalable  and reliable .

Utilize all available hardware.

There are two methods to take backups in oracle

a. Operating system commands to perform backup and SQL or SQL*Plus commands for recovery

b.Using RMAN to perform backup , restore and recovery.

RMAN Environment

a. RMAN executable

RMAN executable are automatically included with oracle installation and as default it is located at $ORACLE_HOME/bin .

b.RMAN target database

Target database is the database which you are going to take backup,restore.A single recovery cataloge* can be used to store metadata of multipe databases.

*Recovery cataloge is a set of tables and views used by RMAN to store the information about the target database and RMAN uses this cataloge to backup,restore and recover the database.

c. RMAN repository 

RMAN repository is the metadata which RMAN uses to store target database information and its backup and recovery operations .This will contain backup set pieces, target database schema, persistent configuration settings etc etc.

d. RMN media management Interface

This will be used for storing backup's in external media like tape drives. RMAN media interface will loads , unloads and labels backup media's .

RMAN Sample Script and its description 

Connecting to the RMAN

We can use different methods to connect to RMAN. Here i am using connecting to the target database using OS credentials as default. You can see mounted target database given as MBDB.

As per the sample script RMAN backup activities are pointed to a log file (/home/oracle/logs/ARTLBK/rmanlogs/backupincremental_0.$BACKUP_DAY.log) where $BACKUP_DAY is the folder for each days back up which is exported as an environment variable initially with the script .

Allocating the channel 

RMAN channel represents a stream of data to a device type from an established server session and backup, restore and recovery operations will be carried out through this established channel. as per our script we are creating 2 channels for the backup channel c1 and channel c2 and mentioned as device type and disk ( we are taking the backup in local disk ) . Also i want the backup should be happen at non default location (/oradata/backup/$BACKUP_DAY) because of the space constrain, so mentioned the same along with channel allocation here .

Backup format 

%d- Name of the backup
%T-Year,Month,Day (YYYYMMDD)
%t-Back up set time stamp which is a 4 byte value
%s-Back up set number and which is used for unique identification of the back up sets.
%p-The piece number with in the back up set and same will be incremented by 1.

Type of backups 

Full Backup- Full back up will back up all data files in the DB as block by block . Using a full back up you can recover the entire at that point of time.

Level1 Backup- This will take the back up of the blocks which are changed from last parent backup (Level0 or Level1). (please check the sample script given above)

Level0 Backup- This is almost identical as full back up except the empty blocks . 

Differential Incremental Backup -  As per this backup RMAN looks for the changed data blocks since from either last  Level0 or Level1backups.

Cumulative Incremental Backup- Same as differential backup incremental backup also takes the changed data blocks from last Level0 or Level1 backup and the exception is if the last backup is an incremental backup, this will take the backup of changes of changes which will reduce the restoration timing.

Also to remove old incremental backups ( becouse i am planning to take full backup on weekly basis) command is given to delete all incremental backups older than 8 days .

Listing the Backups 

You can view the list of backups using 

RMAN> LIST BACKUP; command 

Listing the Archive logs 

Archive logs can be cross checked using 

RMAN> LIST COPY; command 

Configuring the back up script in crontab 

I have configured the back up script in crontab which will be run at 2:30 AM every day

                                  DNS configuration in linux

Here i am giving you a basic idea about DNS (bind) configuration in linux server's . I have configured the bind package in Cent OS 5.4 version .

1. First we will check main packages required for bind configuration. I am listing the package names below
     a. bind-9.3.4-10.pl.el5
     b.bind-libs-9.3.4-10.pl.el5
     c.bind-chroot-9.3.4.-10.pl.el5

2. Once you install these packages you can see the main configuration file for the DNS server called named.conf. The purpose of this file to define the zone files to be used for each of your websites . Default location of this file will be /etc and you have to keep the copy of the same in /var/named/chroot/etc also for security purpose . Sample configuration is given below for reference .

3.  Details of the main configuration files for DNS and its locations are given below

File	Purpose	BIND chroot Location	Regular BIND Location
named.conf	Tells the names of the zone files to be used for each of your website domains.	/var/named/chroot/etc	/etc
rndc.key rndc.conf	Files used in named authentication	/var/named/chroot/etc	/etc
zone files	Links all the IP addresses in your domain to their corresponding server	/var/named/chroot/var/named	/var/named

4.  Here as per our configuration zone files are vm.linux.com.zone ( forward lookup zone) and 0.1.168.192.in.addr.arpa (reverse lookup zone).

As per this configuration you can see the TTL ( time to leave ) value is 86400 seconds . This value indicates the time where the caching name server's will keep the answer from authority server , so the load to the authority server will be reduced .

Details of the forward look up zone file configuration is given bellow

Field	Description
Name	The root name of the zone. The “@” sign is a shorthand reference to the current origin (zone) in the /etc/named.conf file for that particular database file.
Class	There are a number of different DNS classes. Home/SOHO will be limited to the IN or Internet class used when defining IP address mapping information for BIND. Other classes exist for non Internet protocols and functions but are very rarely used.
Type	The type of DNS resource record. In the example, this is an SOA resource record. Other types of records exist, which I’ll cover later.
Name-server	Fully qualified name of your primary name server. Must be followed by a period.
Email-address	The e-mail address of the name server administrator. The regular @ in the e-mail address must be replaced with a period instead. The e-mail address must also be followed by a period.
Serial-no	A serial number for the current configuration. You can use the date format YYYYMMDD with an incremented single digit number tagged to the end. This will allow you to do multiple edits each day with a serial number that both increments and reflects the date on which the change was made.
Refresh	Tells the slave DNS server how often it should check the master DNS server. Slaves aren’t usually used in home / SOHO environments.
Retry	The slave’s retry interval to connect the master in the event of a connection failure. Slaves aren’t usually used in home / SOHO environments.
Expiry	Total amount of time a slave should retry to contact the master before expiring the data it contains. Future references will be directed towards the root servers. Slaves aren’t usually used in home/SOHO environments.
Minimum-TTL	There are times when remote clients will make queries for subdomains that don’t exist. Your DNS server will respond with a no domain or NXDOMAIN response that the remote client caches. This value defines the caching duration your DNS includes in this response.

Different types of records on forward look up zone file is given bellow

Record Type	Name Field	Class Field2	Type Field	Data Field
NS	Usually blank1	IN	NS	IP address or CNAME of the name server
MX	Domain to be used for mail. Usually the same as the domain of the zone file itself.	IN	MX	Mail server DNS name
A	Name of a server in the domain	IN	A	IP address of server
CNAME	Server name alias	IN	CNAME	"A" record name for the server
PTR	Last octet of server’s IP address	IN	PTR	Fully qualified server name

5. Same way reverse look up configuration file is also located in the same location ( in our case it will be 0.1.168.192.in.addr.arpa which is located at /var/named/chroot/var/named )

6.    After configuring these zone files we can restart the named service as given below

7.     Login to the different server which is located at the same network and add the name server details in /etc/resolve.conf file . Format is given below

8.   After configuring the name server details you can test the DNS with below mentioned command

#dig FQDN ( Fully Qualified Domain Name) SOA

Sample output is given below

                                       

Your DNS configuration is successful .