Asm Md 6q5g23

ASM MD_BACKUP and MD_RESTORE:-->

md_backup command and md_restore are used to obtain the SQL statements to recreate the disk groups and all the dependencies such as directories, templates, aliases and disk group attributes. 　 When we restore RMAN backup to a lost diskgroup or to a different server we will get errors something like ORA-01119: error in creating database file ... ORA-17502: ksfdcre:4 Failed to create file ... ORA-15001: diskgroup "DATA" does not exist or is not mounted

md_backup An ASM instance doesn’t store data. It maintains the storage metadata such as the names of the disk groups, directories, and so on and stores this metadata in the disk headers. This means that if there is a disk crash and we lose the disk headers, we’re in trouble. we can use RMAN to restore a backup for the database itself, but we’ll have to first re-create the ASM disk groups and directories. If we haven’t kept careful records, we’re in trouble again. Even if we have the records, we must still take the time to re-create the necessary ASM metadata. In Oracle Database 11g, the ASMCMD utility is extended to provide ASM metadata backup and restore functionality through the md_backup and md_restore commands. This functionality is known as the ASM metadata backup and restore (AMBR). The goal is to enable you to easily re-create an ASM disk group with an identical template and alias directory structure, using the backup of the ASM metadata. This eliminates the need for manually re-creating the disk groups and the necessary directories or templates following the loss of an ASM disk group. The new md_backup option in Oracle Database 11g lets you perform an ASM metadata backup for a disk group. The command will back up into a backup text file, disk group metadata including fail groups, disks, attributes, aliases, and templates. Here’s the syntax of the md_backup command: md_backup [-b ] [-g ' , ,...'] The following lists the various flags and their meanings: Fla g

Description

-b

Specifies the location in which you want to store the intermediate backup file.

-g

Specifies the diskgroup name that needs to be backed up.

The -b option lets you specify the backup file to store the information. By default, the filename is ambr_backup_intermediate_file. The -g option lets you specify the disk groups to back up. The command backs up all disk groups by default. md_backup is ran from the ASMCMD> prompt. It very simply creates a file that is a backup of your metadata, for all of your disk groups, or just a few if you want to specify. By default, it writes to the current directory and

backs up all of the mounted disk groups header files. Here’s an example showing how to use the md_backup command to back up a single disk group named dsk1. ASMCMD> md_backup -b /tmp/dgbackup070222 -g dsk1 The md_backup command shown here uses the -g option to create a backup of the disk group dsk1 and saves it in the /tmp/ dgbackup070222 file. The -b option specifies that the backup information containing the ASM metadata be recorded in the file named asmblp1 instead of in the default file named ambr_backup_intermediate_file. md_restore The md_restore command is the counterpart of the md_backup command and helps us restore the ASM metadata for a disk group. Before we can restore data files in a disk group, we must first restore the disk group using this command. The md_restore command has the following syntax: md_restore -b [-li] [-t (full)|nodg|newdg] [-f <sql_script_file>] [-g ' , ,...'] [-o ' : ,...'] The following lists the various flags and their meanings:

Flag

Description

-b

Reads the metadata information from backup_file.

-l

Prints the messages to a file.

-i or --silent

If md_restore encounters an error, it will stop. Specifying this flag ignores any errors.

-t

Specifies the type of diskgroup to be created: full - Create diskgroup and restore metadata. nodg - Restore metadata only. newdg - Create diskgroup with a different name and restore metadata, -o is required to rename.

-f or -S

Write SQL commands to sql_script_file instead of executing them.

-g or -G

Select the diskgroups to be restored. If no diskgroups are defined, then all diskgroups will be restored.

-o

Rename diskgroup old_dg_name to new_dg_name.

We can initiate the creation of a disk group as well as restore its metadata by executing the md_restore command. The following examples show how to use this command in various scenarios: Restoring a disk group from the backup script and creating a copy: ASMCMD> md_restore -t full -g asmdsk1 -i backup_file Restoring an existing disk group’s metadata:

ASMCMD> md_restore -t nodg - asmdsk1 -i backup_file Restoring a disk group and creating a new disk group: ASMCMD> md_restore -t newdg -o 'DGNAME=asmdsk1:asmdsk2' -i backup_file The md_restore command restores the disk groups, creates the attributes such as disk_repair_time, modifies the templates, and creates the directories. It’s important to understand that any data in the disk groups will be lost, however. The md_restore command creates a disk group and the directories without any data. The md_restore uses the backup file created by md_backup command, which backs up just the ASM metadata. You must use your RMAN database backups to restore the information on the re-created disk groups. The following md_restore command example specifies the -f flag to create a text file with the commands to create the disk groups, directories, and so on. ASMCMD> md_restore -b dgroup1.backup -t full -f create_dgroup1.sql You can execute the md_restore command with the -f option on a regular basis to maintain a record of the ASM metadata.

This script will help us to take metadata backup dtm='date +%d%m%y%H%M%S' LOG_FILE=/tmp/asm_backup.${dtm}

rm /app/oracle/TEST/backup/export/asm_dg.backup HOSTNAME='hostname' if [ -s /etc/oratab ] ; then ORATAB=/etc/oratab elif [ -s /var/opt/oracle/oratab ] ; then ORATAB=/var/opt/oracle/oratab elif [ -s /etc/opt/oracle/oratab ] ; then ORATAB=/etc/opt/oracle/oratab else echo "ORATAB is missing" 2>&1 1>> $LOG_FILE cat $LOG_FILE exit 1 fi cat ${ORATAB}|awk -F\# '{print $1}'|grep -v '^$'|awk -F\: '{print $1" "$2" "$3}' |while read ORACLE_SID ORACLE_HOME BOOT_FLAG do if [ "${ORACLE_SID}" = "+ASM" -a "${BOOT_FLAG}" = "Y" ] ; then export ORACLE_SID export ORACLE_HOME export BOOT_FLAG PATH=$ORACLE_HOME/bin:$PATH export PATH asmcmd lsdg asmcmd md_backup -b /app/oracle/TEST/backup/export/asm_dg.backup #ASMCMD> md_restore -t full -g RECOVER /tmp/dg.backup fi done

NOTE:- it will not restore datafile or any other files which was there on that diskgroup we'll have to use RMAN to

restore those missing files.