Oracle Database Administration for Microsoft SQL Server DBAs part 18 pps

Viewing Backups RMAN has a LIST command that will return the backup sets that are present in the catalog or control file.. This means that a copy was included in the backup set and is al

this will take all of the application databases and copy them over to the new database server

Managing Backups

Managing backups is not just about purging and maintaining the retention policy, but also about knowing which backups are available for restores Oracle provides several ways to get information about backup sets

Viewing Backups

RMAN has a LIST command that will return the backup sets that are present

in the catalog or control file The listing shows the different backup pieces and details, including the checkpointed SCN, the date, full or incremental, and tablespaces that were backed up In the following example, the archive logs were included as part of the full backup, so they are also listed

RMAN> list backup;

using target database control file instead of recovery catalog

List of Backup Sets

===================

BS Key Type LV Size Device Type Elapsed Time Completion Time

- - - -

BP Key: 13 Status: AVAILABLE Compressed: NO Tag: TAG20100308T200144

Piece Name:

E:\APP\FLASH_RECOVERY_AREA\MMDEV1\BACKUPSET\2010_03_08\

O1_MF_NNNDF_TAG20100308T200144_5SCC0GDZ_.BKP

List of Datafiles in backup set 13

File LV Type Ckp SCN Ckp Time Name

-

1 Full 1760175 08-MAR-10 D:\ORADATA\MMDEV1\SYSTEM01.DBF

2 Full 1760175 08-MAR-10 D:\ORADATA\MMDEV1\SYSAUX01.DBF

3 Full 1760175 08-MAR-10 D:\ORADATA\MMDEV1\UNDOTBS01.DBF

4 Full 1760175 08-MAR-10 D:\ORADATA\MMDEV1\USERS01.DBF

BS Key Type LV Size Device Type Elapsed Time Completion Time

- - - -

BP Key: 14 Status: AVAILABLE Compressed: NO Tag: TAG20100308T200144

Piece Name: E:\APP\FLASH_RECOVERY_AREA\MMDEV1\BACKUPSET\2010_03_08\ O1_MF_NCSNF_TAG20100308T200144_5SCC2YYM_.BKP

SPFILE Included: Modification time: 08-MAR-10

SPFILE db_unique_name: MMDEV1

Control File Included: Ckp SCN: 1760265 Ckp time: 08-MAR-10

BS Key Type LV Size Device Type Elapsed Time Completion Time

- - - -

BP Key: 15 Status: AVAILABLE Compressed: NO

Tag: TAG20100312T054615

Piece Name:

E:\APP\FLASH_RECOVERY_AREA\MMDEV1\BACKUPSET\2010_03_12\

O1_MF_NCSNF_TAG20100312T054615_5SNBH7Z5_.BKP

SPFILE Included: Modification time: 12-MAR-10

SPFILE db_unique_name: MMDEV1

Control File Included: Ckp SCN: 1905411 Ckp time: 12-MAR-10

BS Key Size Device Type Elapsed Time Completion Time

- - - -

-16 58.13M DISK 00:00:09 12-MAR-10

BP Key: 16 Status: AVAILABLE Compressed: NO

Tag: TAG20100312T054803

Piece Name:

E:\APP\FLASH_RECOVERY_AREA\MMDEV1\BACKUPSET\2010_03_12\

O1_MF_ANNNN_TAG20100312T054803_5SNBHRFM_.BKP

List of Archived Logs in backup set 16

Thrd Seq Low SCN Low Time Next SCN Next Time

- - -

-1 35 1757126 08-MAR-10 1782135 09-MAR-10

1 36 1782135 09-MAR-10 1802422 09-MAR-10

1 37 1802422 09-MAR-10 1828159 10-MAR-10

1 38 1828159 10-MAR-10 1853573 10-MAR-10

1 39 1853573 10-MAR-10 1879239 11-MAR-10

1 40 1879239 11-MAR-10 1902061 12-MAR-10

1 41 1902061 12-MAR-10 1905455 12-MAR-10

To list the details about the archive logs, you can use the sequence

number or SCN

RMAN> list archivelog sequence=36;

List of Archived Log Copies for database with db_unique_name MMDEV1

=====================================================================

Key Thrd Seq S Low Time

- - -

-18 1 36 A 09-MAR-10

Name:

E:\APP\FLASH_RECOVERY_AREA\MMDEV1\ARCHIVELOG\2010_03_09\

O1_MF_1_36_5SDDN6X8_.ARC

17 1 36 A 09-MAR-10

Name:

This example shows two archive log files with the same sequence number This means that a copy was included in the backup set and is also still in the archive log file on the database server This is the case when the DELETE ALL INPUToption isn’t used with the backup command But the archive logs can also be cleared out another way: by being expired and deleted, as discussed in the next section

In OEM, you can see the same backup set listing on the Backup Sets tab

of Manage Current Backups, as shown in Figure 6-9 This page also offers the options to catalog additional files, so if a backup was taken and not recorded in the catalog, you can add those files, cross-check all of the archive logs and backups, delete obsolete files, and expire obsolete files Data dictionary views and recovery catalog tables also provide views into the backup sets, to help manage backups and know which backups are available for restoring These are also good places to check to make sure backups are running properly

FIGURE 6-9. Managing backups in OEM

In the RMAN catalog, RC_DATABASE has the list of databases that are

registered in the catalog RC_BACKUP_SET has the completion time of the

backup, type of backup, and some additional information It might seem

like duplicate information, but remember that the RMAN catalog can keep

the information for multiple databases, so a report can be run for all of the

databases in the catalog The data dictionary view v$backup_set has

the same details, but it is valid for only the database server, not all of the

databases registered in the catalog

The scripts are also stored in the RMAN catalog The RC_STORED_

SCRIPT_LINEtable contains details about the scripts that are scheduled

Other tables that might be useful are RC_BACKUP_SET_DETAILS, RC_

BACKUP_FILES, and RC_RMAN_BACKUP_JOB_DETAILS The

corresponding data dictionary views are v$backup_datafile,

v$backup_set_details, and v$rman_backup_job_details

You can build reports from these tables outside OEM or RMAN to

provide details about the backups that are running against one of the

database servers or multiple databases (from the RMAN catalog)

Purging Obsolete Files

Keeping the catalog a manageable size is part of backup maintenance In

SQL Server, you can handle this when you schedule a database backup by

setting an expire time on the backup, by number of days or on a specific

date In Oracle, the parameters REDUNDANCY and RECOVERY WINDOW set

the number of backups and number of days for retention policies Table 6-2

shows the options for expiring and deleting backup files in SQL Server and

Oracle

You can run reports to get the status of the backup pieces, including

which ones have been marked obsolete by the retention policy, deleted, or

expired First, run a cross-check to check the files that have been deleted or

marked obsolete Then run the RMAN DELETE OBSOLETE command to

remove the files

RMAN> CROSSCHECK BACKUP;

RMAN> CROSSCHECK ARCHIVELOG ALL;

RMAN> DELETE EXPIRED BACKUP;

If not deleting archive logs as they are backed up,

delete from file system via DELETE

RMAN> DELETE ARCHIVELOG ALL BACKED UP 2 TIMES;

It is possible to override the defaults for retention policies as well as force the backups to be deleted by using the RMAN DELETE FORCE

command

Backing Up and Restoring Objects

With SQL Server, it is typical to restore a database to get a copy of just the objects that are needed With Oracle, restoring the database is normally to restore the full system, but there are utilities available to pull out just the objects by schema, or even at the table level This allows you to secure backups for these objects or copy them to another system, perhaps to refresh

a test environment with just the needed schema or tables

Copying Objects at the Table

and Schema Level

Using a SQL statement, you can create a table from an existing table for a quick backup of a table before data changes A backup table can be defined (such as CREATE table TAB_BACKUP AS select * from TAB_PROD) with tablespaces, no logging (to avoid some of the logging in the redo logs), and with some of the other table options The table will not include any of

Expire Part of backup job or script

parameters EXPIREDATE or RETAINDAYS(number of days

or on a date)

RMAN parameters REDUNDANCYand RECOVERY WINDOW (number of days or number of backups) Delete (from

msdb/catalog)

sp_delete_backuphistory DELETE EXPIRED

Delete expired

backup files

Maintenance Cleanup task DELETE OBSOLETE

BACKUP ARCHIVELOGS DELETE ALL INPUT

TABLE 6-2. Delete and Expire Backup Options in SQL Server and Oracle

the indexes, constraints, or triggers that might be on the “real” table, but it

will have the same datatypes and the same data A WHERE clause can also

be defined in the CREATE table AS statement to capture data that might

be archived or deleted, as an extra security blanket

SQL Server also has a couple of utilities to pull out table-level data as

well as the table definitions The bcp utility could be used copy table

objects on the SQL Server side

Oracle has the Data Pump utility, which handles both exports and

imports, as well as older EXP and IMP utilities For example, you might

export a schema with just the simple EXP, and remap the schema to a new

user to refresh a test schema Chapter 5 covered some other tools, such as

SQL Developer, that can pull the structure information for tables and also

help copy objects to another environment or schema However, the Data

Pump utilities are easier to use and generally perform better, so we’ll take a

closer look at them here

Using Data Pump

Since Oracle Database 10g, the new improved version of the export and

import utilities is Data Pump You can set up a Data Pump export job to

allow you to recover just a table or another object, such as a view or stored

procedure The exports include the Data Definition Language (DDL), which

creates the structures of the tables, procedures, trigger, indexes, views, and

other objects Exports can also be done without data, to provide just these

structures, which you can then copy to another schema or save as a backup Data Pump does require some setup and permissions Since the export file

is being written out, it needs a directory for the file to write to Directories are

defined in the database, and permissions are given to read or write to the files for users that need to perform these tasks If the exports and imports are being

used only by the DBA for backups or refreshes, then these are privileged

accounts

A job is created with each Data Pump execution A name can be

specifically given to a job to be able to view its progress The dba_

datapump_jobsview shows the jobs

The Data Pump job can also export the full database by setting the

parameter FULL=Y, and then be used to restore only a schema or table

Tablespaces and queries can also be exported Even if you’re exporting a

full schema or tablespace, you can exclude a table or object by using the

EXCLUDEparameter This is useful for skipping over history tables or very

large tables that might be used only for reading or reporting To view the

different parameters available for these utilities from the command line, execute expdp help=Y

Here are a few examples of creating a directory and exporting and importing with Data Pump from the command line:

SQLPLUS> create directory DATAPUMP_DIR

as '/oraexport/DB01/dpdump';

SQLPLUS> grant read, write on directory DATAPUMP_DIR to MMTEST;

## To run an datapump export from the command line

## This will export a couple of tables

> expdp mmprod/mmpasswd schemas=MMPROD tables=TAB1,TAB2

directory=DATAPUMP_DIR dumpfile=exp_tables.dmp log=Exp_tables.log

## This will export one schema

> expdp mmprod/mmpasswd schemas=MMPROD directory=DATAPUMP_DIR dumpfile=exp_mmprod.dmp log=Exp_mmprod.log

## To run a datapump import to refresh the

## test schema from the dump

> impdp mmtest/mmpasswd remap_schema=MMPROD:MMTEST

directory=DATAPUMP_DIR file=exp_mmprod.dmp log=Imp_mmtest.log

Just as you can schedule RMAN backup jobs in OEM, you can also schedule Data Pump jobs Figure 6-10 shows the selection of an export to a

FIGURE 6-10. Choosing what to export in OEM

file, which is found under the Data Movement tab The options are to export the database, schemas, tables, or tablespace

After selecting what to export, you can get an estimate of the disk space

and set other parameters, as shown in Figure 6-11 Estimating the disk space would be useful in planning the directory space for the job, especially if you’re

keeping a couple of copies of the export files You can choose whether to use the actual data blocks or the table statistics to gather this information You select the directory here, or you can create one if you are using an account with the appropriate permissions (the actual file name for the export file is specified in

the next step) You also can choose whether or not you want a log of the export The advanced options allow for selections of data and structures, just data, or

just structures Objects can be either included or excluded—choosing the one

that makes the shortest list is recommended

FIGURE 6-11. Defining an export job in OEM

Figure 6-12 shows the OEM options for scheduling a Data Pump job After you have set up the Data Pump job, even if it is a one-time run of the job, it will be listed in the job activity for the export jobs and other scheduled jobs You can monitor it by clicking its name (DAILY_EXP in the example in Figure 6-12)

Another option available in OEM is to set up a connection to a different database through a database link when importing, as shown in Figure 6-13 This would be run from the server to which you want to copy the objects, and the database link would be created to the source database

NOTE

I am sure I don’t need to warn you about being

careful with mixing production and test

environments with links Sometimes it is

necessary to be able to refresh the test

environment This chapter has given you some

examples of how to recover the database if

something goes wrong

FIGURE 6-12. Scheduling a Data Pump job in OEM

Protecting Users from Users

Much of the thought put into backups and recovery is to protect the system

from hardware issues or even disasters, but you also need to consider what

damage people can do Developers, users, and DBAs use the database

environment for development, testing, running applications, making changes,

and just doing their jobs As a DBA, you probably confirm which environment

you are logged in to before making a change You probably run an extra

backup just to give yourself that extra protection in case something goes wrong But other users may not be so cautious They may accidentally log in to the

wrong environment and drop a table or change a stored procedure Fortunately, Oracle offers some features to assist in protecting users from themselves

Recycle Bin

How many times have you pulled something out of the Windows Recycle Bin after deleting it? The Oracle recycle bin works the same way with tables that

have been dropped For example, if you were refreshing a couple of tables,

and realized you dropped the wrong tables, you can retrieve those objects

FIGURE 6-13. Importing objects with OEM