OCA /OCP Oracle Database 11g A ll-in-One Exam Guide- P65 doc

OCA/OCP Oracle Database 11g All-in-One Exam Guide 596 with DELETE OBSOLETE, which will remove the records of any such backups from the repository and physically remove the backup files from disk or tape. For example, RMAN> report obsolete; will apply the configured retention policy and list all copies and backup sets that are no longer required. Then, RMAN> delete obsolete; will remove the backups deemed surplus to requirements. RMAN> report obsolete redundancy 2; lists all backups that take the number of backups of an object to three or more. Then to remove the superfluous backups, RMAN> delete obsolete redundancy 2; The DELETE command can also be used to remove individual backups, by number or by tag: RMAN> delete backupset 4; RMAN> delete copy of datafile 6 tag file6_extra; Archival Backups In Oracle terminology, an archival backup is a backup that you want to keep long term, possibly forever. It will not usually be necessary to recover from an archival backup: it should be possible to restore it in order to recreate the database as it was at the time the backup was made, but you won’t want to apply archived logs to it to bring it further forward in time. Often, archival backups are made purely to satisfy legislation regarding retention of records; they have little or no technical significance. An archival backup does not count toward compliance with the configured retention policy, and neither will it be deleted automatically by a DELETE OBSOLETE command. Even though it will not usually be necessary to keep the archive logs needed to recover an archival backup up to the present day, if the archival backup is an open backup then it will be necessary to keep all the archive logs generated while the backup was being taken. This is because they will be needed to make the open backup consistent, in the event of having to restore it. The syntax to create an archival backup is BACKUP KEEP { FOREVER | UNTIL TIME 'date_expr' } [ RESTORE POINT rsname ] ; The clause defining what to back up can be anything: a datafile, a tablespace, the whole database, incremental, compressed, encrypted, and so on. It can be directed to either tape or disk. However, usually, the only sensible backup target is a full backup of the whole database, and it will probably be directed through a tape channel to a tape library. The date expression can be an actual date or a calculation. An example is Chapter 15: Back Up with RMAN 597 PART III backup database as compressed backup set keep until time 'sysdate + 90' restore point quarterly_backup ; This command will write out a compressed backup, which will be considered obsolete (and therefore deletable) after 90 days. If the database is open at the time, the relevant archivelogs will be included. The Dynamic Performance Views A number of views populated from the target database controlfile can be used to report on RMAN’s backups. By querying these, you can develop your own reports, rather than relying on RMAN’s LIST command. View Displays v$backup_files One row for each file that has been backed up, which may be a datafile, the spfile, the controlfile, or an archive log. Also, one row for each piece that RMAN has created. The column FILE_TYPE distinguishes which type of file the row refers to. v$backup_set One row per backup set v$backup_piece One row per backup piece v$backup_redolog One row for each archived log that has been backed up v$backup_spfile One row for each backup that has been made of the spfile v$backup_datafile One row for backup of a datafile v$backup_device Names of SBT devices that have been linked to RMAN v$rman_configuration One row for every configuration setting, excluding all those on default Join columns in the various views will let you construct comprehensive reports on what has been backed up, where the backups are located, and the size and type of each backup. Crosschecking Backups The information used by the RMAN commands REPORT and LIST, and the information displayed in the dynamic performance views, is drawn from the RMAN repository: data stored in the controlfile of the target database. It says nothing about reality—whether the backup files actually still exist. To confirm that the backups do exist, use the CROSSCHECK command. For example: RMAN> crosscheck backup of database; using channel ORA_DISK_1 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/flash_recovery_area/orcl/backupset/2008_10_20/ o1_mf_nnnd0_backup_orcl_000002_1_4hs9zcn8_.bkp RECID=5 STAMP=668623611 crosschecked backup piece: found to be 'AVAILABLE' backup piece handle=/u01/app/oracle/flash_recovery_area/orcl/backupset/2008_10_21/ o1_MF_nnnd1_tag20081020t165738_4hsbmv14_.bkp RECID=8 STAMP=668624267 Crosschecked 2 objects OCA/OCP Oracle Database 11g All-in-One Exam Guide 598 This command queries the repository to find details of what whole backups have been made of the database, and then goes to the storage device(s) to see if the pieces do in fact exist. For pieces on disk, the disk directory is read and the file header validated; for pieces on tape, only the tape directory is read. Any pieces that no longer exist are flagged in the repository as EXPIRED. An expired backup will not be considered by RMAN when it works out how to carry out a restore and recover operation. In some circumstances (such as if a file system or a tape drive is taken offline), a crosscheck may mark many backups as expired; rerunning the crosscheck when the device is brought back into use will reset their status to AVAILABLE. A related command is RMAN> delete expired; This command will not delete any files from disk. It will, however, remove from the repository all references to backups previously marked EXPIRED by a crosscheck. At many installations, the tape library will automatically delete files according to their age: if this is happening, then a crosscheck followed by DELETE EXPIRED will update the RMAN repository to make it aware of what has happened. EXAM TIP A DELETE EXPIRED command does not delete any files, it only updates the RMAN repository. A DELETE OBSOLETE will delete files and update the repository accordingly. Exercise 15-4: Manage Backups After putting the RMAN configured settings back to defaults, use the BACKUP, LIST, REPORT, and DELETE commands to create and remove backups. 1. Connect to your database with SQL*Plus, and query the state of your flash recovery area: select * from v$flash_recovery_area_usage; 2. Connect to your database with RMAN using operating system authentication: rman target / 3. Ensure that your retention policy is set to the default, REDUNDANCY 1: RMAN> configure retention policy clear; 4. Delete all your backup sets and image copies: RMAN> delete backupset all; RMAN> delete copy all; If any backups are listed, enter YES to confirm deletion. 5. List the items that need backing up, according to the configured retention policy: RMAN> report need backup; This will list all your datafiles. 6. Choose a datafile, and back it up. In the example that follows, file 6 has been chosen: RMAN> backup datafile 6; Chapter 15: Back Up with RMAN 599 PART III Repeat the command to take a second backup of the same file. 7. Repeat the command from Step 4. The file that has been backed up will not be listed. 8. In your SQL*Plus session, rerun the query from Step 1 and note that there is some reclaimable space. 9. List your backups with RMAN> list backup; 10. Report and delete the backup that is unnecessary according to the configured retention policy: RMAN> report obsolete; RMAN> delete obsolete; This will remove the first backup made in Step 5, because it is redundant following the creation of the second backup. 11. In your SQL*Plus session, rerun the query from Step 1 and note the difference in usage. Two-Minute Drill Create Consistent Database Backups • If the database is in noarchivelog mode, then whole consistent backups (full or incremental) are the only type of backup possible. • An RMAN-consistent backup is taken with the database in mount mode, following a clean shutdown. Back Up Your Database Without Shutting It Down • An open backup of the database must also include a backup of the archivelog files, either included in the same backup set or in a separate backup set. • Open backups, for which the database must be in archivelog mode, can be whole or partial, full or incremental. Create Incremental Backups • A level 1 incremental or cumulative backup cannot be based on a full backup, only a level 0 incremental backup. • Unless block change tracking is enabled, an incremental backup must scan the entire database. • An RMAN backup set, whether full or incremental, never includes unused blocks. OCA/OCP Oracle Database 11g All-in-One Exam Guide 600 Automate Database Backups • Oracle Enterprise Manager (Database Control or Grid Control) can schedule the running of backup jobs. Manage Backups, View Backup Reports, and Monitor the Flash Recovery Area • The LIST command shows what backups have been made, and the REPORT command shows what backups are needed or are redundant. • The flash recovery area is the default destination for RMAN disk backups. • RMAN can automatically delete files considered to be obsolete from the flash recovery area. Define, Apply, and Use a Retention Policy • The backup retention policy may be based on redundancy (keeping a certain number of copies) or recovery window (guaranteeing the possibility of point- in-time recovery). • Backups considered obsolete according to the retention policy can be automatically deleted. Create Image File Backups • An image copy is identical to the source file. • Image copies can be directed only to disk. • Image copies can be made of datafiles, the controlfile, and archivelog files. Create a Whole Database Backup • A whole RMAN backup is the full set of datafiles, the spfile, and the controlfile. • RMAN does not back up online logs, tempfiles, or the password file. Enable Fast Incremental Backup • Changed blocks are tracked by the change tracking writer process, the CTWR. • The change tracking file is automatically managed; the DBA can choose only its name and location. Create Duplex Backups and Back Up Backup Sets • The COPIES keyword instructs RMAN to create multiple copies of backup sets or images. • Backup sets can be backed up into more backup sets with BACKUP BACKUPSET. Chapter 15: Back Up with RMAN 601 PART III • The BACKUP RECOVERY AREA and BACKUP RECOVERY FILES commands can only write to a tape destination. Create an Archival Backup for Long-Term Retention • The KEEP keyword creates a backup to which the retention policy will not be applied. • If the archival backup is an open backup, all necessary archive logs will be automatically included. Create a Multisection, Compressed, and Encrypted Backup • The SECTION keyword lets multiple channels back up one file concurrently. • Backup sets can be compressed (unlike image copies), by default with the BZIP2 algorithm. • Encryption can be enabled using either a wallet or a password. Report on and Maintain Backups • RMAN will automatically delete backups from the flash recovery area considered to be obsolete, if the flash recovery area is full. • The DELETE OBSOLETE command will delete all backups considered obsolete, whether in the flash recovery area or not. Configure Backup Settings • RMAN’s default behavior is modified with the CONFIGURE command. • Configured defaults are stored in the target database’s controlfile, as part of the RMAN repository. Allocate Channels to Use in Backing Up • Channels are of type disk or SBT (or SBT_TAPE). SBT channels are only available if a suitable device driver has been installed. • Parallelize backups by launching multiple channels, using ALLOCATE CHANNEL commands within a run block or by configuring a default. Configure Backup Optimization • Optimization only applies to identical files: archivelogs, or datafiles that are either offline or read-only. • Optimization is not enabled by default, and if enabled is reliant upon the retention policy currently in effect. OCA/OCP Oracle Database 11g All-in-One Exam Guide 602 Self Test 1. What file types can be backed up by RMAN? (Choose four answers.) A. Archive log files B. Controlfile C. Online log files D. Password file E. Permanent tablespace datafiles F. Server parameter file G. Static parameter file H. Temporary tablespace tempfiles 2. If your database is in noarchivelog mode, which of the following is possible? (Choose the best answer.) A. Online backups B. Partial backups C. Incremental backups D. All of the above, but only if you use RMAN 3. RMAN backup sets are smaller than RMAN image copies because . . . . (Choose the best answer.) A. They always use compression. B. They always skip unused blocks. C. They never include tempfiles. D. They can be written directly to tape. 4. Which of the following statements are correct about RMAN offline backup? (Choose all correct answers.) A. The database must be in NOMOUNT mode. B. The database must be in MOUNT mode. C. The backup will fail if the shutdown mode was SHUTDOWN IMMEDIATE. D. Noarchivelog databases can only be backed up offline. E. Archivelog databases cannot be backed up offline. F. Offline backups can be incremental. 5. You need to back up the control file while the database is open. What will work? (Choose the best answer.) A. The controlfile can be included in an RMAN backup set, but not backed up as an image copy. Chapter 15: Back Up with RMAN 603 PART III B. The ALTER DATABASE BACKUP CONTROLFILE TO TRACE command will make an image copy of the controlfile. C. You cannot back up the controlfile while it is in use—it is protected by multiplexing. D. None of the above. 6. You perform a full backup on Sunday, an incremental level 0 backup on Monday, an incremental level 1 differential backup on Tuesday, an incremental level 1 cumulative backup on Wednesday, and an incremental level 1 cumulative backup on Thursday. Which blocks will be included in the Thursday backup? (Choose the best answer.) A. All blocks changed since Sunday B. All blocks changed since Monday C. All blocks changed since Tuesday D. All blocks changed since Wednesday 7. If you issue this RMAN command, backup incremental level 1; and there is no level 0 backup, what will happen? (Choose the best answer.) A. The command will fail. B. The incremental backup will be based on the most recent full backup. C. RMAN will perform a level 0 backup. D. RMAN will perform a level 1 cumulative backup of all blocks that have ever been changed. 8. What processes must be running if an RMAN backup scheduled within the Oracle environment is to run? (Choose two correct answers.) A. The database instance processes must be running, in MOUNT or OPEN mode. B. The database instance processes must be running, in at least NOMOUNT mode. C. The Enterprise Manager processes (either Database Control or the Grid Control agent) must be running. D. The operating system scheduler must be running. 9. What is true about the CROSSCHECK command? (Choose the best answer.) A. CROSSCHECK will check the validity of the backup pieces. B. CROSSCHECK will delete references to files that no longer exist. C. CROSSCHECK will verify the existence of backup set pieces. D. CROSSCHECK only works with backup sets, not image copies. OCA/OCP Oracle Database 11g All-in-One Exam Guide 604 10. If the volume of data in the flash recovery area has reached the limit defined by DB_RECOVERY_FILE_DEST_SIZE, what will happen when RMAN attempts to write more data to it? (Choose the best answer.) A. If AUTOEXTEND has been enabled and the MAXSIZE has not been reached, the flash recovery area will extend as necessary. B. The operation will fail. C. This will depend on whether warning and critical alerts have been enabled for the flash recovery area. D. RMAN will automatically delete OBSOLETE backups. E. RMAN will automatically delete EXPIRED backups. Self Test Answers 1. þ A, B, E, and F. These are the database file types that the Recovery Manager can back up and restore. ý C, D, G, and H. RMAN will never back up online redo logs or tempfiles because it is not necessary to back them up, and it cannot back up a static parameter file or the external password file. 2. þ C. RMAN can make incremental backups no matter what mode the database is in. ý A, B, and D. Whatever method you use, backups of a noarchivelog mode database cannot be either partial or online. 3. þ B. A backup set will never include blocks that have never been used. ý A, C, and D. A is wrong because compression is an option, not enabled by default. C is wrong because it applies to image copies as well as backup sets. D is wrong because it is not relevant: an image copy can’t go to tape, because if it did, it wouldn’t be an image. 4. þ B, D, and F. Offline backups must be done in mount mode. This is the only backup type for a noarchivelog mode database, but it can be incremental. ý A, C, and E. A is wrong because the database must be mounted, or RMAN won’t be able to connect to its repository or find the location of the datafiles. C is wrong because an IMMEDIATE shutdown is clean—it is only an ABORT that would cause problems. E is wrong because an archivelog mode database can certainly be backed up offline—it just isn’t necessary. Chapter 15: Back Up with RMAN 605 PART III 5. þ D. A, B, and C are all incorrect. ý A, B, and C. A is wrong because a copy of the controlfile can be created while the database is open, via a read-consistent snapshot. B is wrong because this command will generate a CREATE CONTROLFILE script, not a file copy. C is wrong because the file multiplexing is an additional precaution, not the only one. 6. þ B. A cumulative backup will include all blocks changed since the last level 0 backup. ý A, C, and D. A is wrong because the full backup cannot be used as a base for an incremental backup. C and D are wrong because cumulative backups always go back to the most recent level 0 backup. 7. þ C. RMAN will revert to level 0 in this circumstance. ý A, B, and D. A is wrong because the backup will succeed—though perhaps not in the way you wanted. B is wrong because no incremental backup can be based on a full backup. D is wrong because although the effect described is correct, it will not be recorded as a cumulative backup but as a level 0 backup. 8. þ A and C. The Enterprise Manager processes will run the backup, and the database must be mounted or RMAN will not be able to connect to the repository. ý B, and D. B is wrong because NOMOUNT mode is not enough. D is wrong because Oracle-scheduled backups do not use the operating system scheduler. 9. þ C. The CROSSCHECK command verifies that the repository does accurately reflect reality. ý A, B, and D. A is wrong because CROSSCHECK does not validate whether the backups are good—only whether they exist. B is wrong because CROSSCHECK doesn’t delete references to missing backups; it only flags them as expired. D is wrong because CROSSCHECK confirms the existence of both backup sets and image copies. 10. þ D. Backups that are OBSOLETE according to RMAN’s retention policy will be removed. ý A, B, C, and E. A is wrong because this describes datafiles, not the flash recovery area. B is wrong because the operation will not necessarily fail—it may be possible to free up space automatically. C is wrong because the alert system will only report the problem; it won’t fix it. E is wrong because EXPIRED refers to the status of the backup record in the repository, not the backup itself. . An RMAN backup set, whether full or incremental, never includes unused blocks. OCA/ OCP Oracle Database 11g All-in-One Exam Guide 600 Automate Database Backups • Oracle Enterprise Manager (Database. expression can be an actual date or a calculation. An example is Chapter 15: Back Up with RMAN 597 PART III backup database as compressed backup set keep until time 'sysdate + 90' restore. þ C. RMAN can make incremental backups no matter what mode the database is in. ý A, B, and D. Whatever method you use, backups of a noarchivelog mode database cannot be either partial or online.