This document discusses database backup and recovery concepts including: 1. Mean time between failures and mean time to recover should have high and low values respectively. Database failures can occur due to statements, processes, instances, and user errors. 2. Solutions for failures include adding filespaces, using PMON to recover from backups, restarting instances, and SQL commands like ALTER SYSTEM SWITCH LOGFILE. 3. Views like V$INSTANCE, V$FAST_START_SERVERS, V$BACKUP are queried to obtain database information for managing backups and different types of recovery including time-based, cancel-based, and change-based.

1. AnarGodjaev
BACKUP and RECOVERY
Lsnrctl services [listener01]
Mean_time_between_failures
Mean_time_to_recover
//*should be bigger in value*//
//*should be smaller in value*//
Problem
Statement failure
logic error
insufficient privileges
Process failure
‐user session abnormally terminated
User errors
‐drop table
‐truncate table
‐delete...commit
Instance failure
v$sgastat
- pool
- name
- bytes
v$log
- group_number
- log_sequence_number
- size_of_the_group
- number_of_members
v$logfile
- name
- status
- group
large pool
- backup restore operations
- I/O server processes
- Session memory fro shared users
- Large_pool_size (approximately 2gb)
Rman
- dbwr_io_slaves (integer)
- backup_tape_io_slaves (true|false)
Solution
Statement failure
Add filespace to the tablespace
Pmon
Recover from a backup
Restart the instance

2. AnarGodjaev
SQL> alter system switch logfile;
Alter database db_name rename file ‘...’ to ‘...’;
Fast_start_mttr_target:
expectedmttr specified in seconds amount of the time that has passed since the incremental
checkpoint at the position where the last write to redo log file occured.
Log_checkpoint_interval:
number of redo log file blocks that can exist between an incremental checkpoint and the last
block written to the redo log.
v$instance recovery
recovery_estimated_ios: ‐ recovery_estimated_ios: number of dirty buffers in the buffer cache
actual_redo_blks: - current actual number of redo blocks required for recovery
taret_redo_blks: - current number of redo blocks that must be processed for recovery
log_file_size_redo_blks: - current number of redo blocks required to guarantee that
a log switch doesnt occur before checkpoint.
log_chkpt_timeout_redo_blks:
estimated_mttr: current estimated mean time to recover (mttr). Based on the number of dirty
buffers and redo log blocks.
ckpt_block_writes: number of blocks written by checkpoint writes
v$fast_start_servers
v$fast_start_transactions
rolling forward phase
- set recovery_parallelism<integer>
- use parallel clause in the recover database statement
rolling back phase
‐ set fast_start_parallel_rollback [false | low | high] //low is default
user managed backup and recovery
offline backup – consistant whole database setup

3. AnarGodjaev
SQL> shutdown immediate
!cp<files> /backup/... //control file, datafile, redo log file, password file, parameter file
startup open
online backup – the database should be in archive log mode
SQL> alter tablespace users begin backup
!copy the datafiles
altertablespace users end backup
alter system archivelog current
//archive the unarchivedredologs so that the redo
required to recover the tablespace backup is achieved query the following views.
v$backup
//file,status,change,time
v$datafile_header
SQL> alter database end backup;
Alter database datafile ‘...’ end backup;
Alter tablespace<tablespace name> read only;
!backup the datafiles
Alter tablespace<tablespace name> read write;
Logging and nologging
Set database to nologging for faster data loading After this you should backup the datafiles
SQL> Alter database backup controlfile to ‘control01.bck’;
Alter database backup controlfile to trace;
Obtain database information by quering the following views
v$datafile
v$controlfile
v$logfile
dba_datafiles
user managed recovery
- time based
- cancel based
- change based
recovery steps
1‐ damaged files are restored from backup
2‐ changes from archived redo logs or online redo logs are applied if necessary

4. AnarGodjaev
3‐ the database may now contain commited and uncommited changes
4‐ the undo block are used to rollback any uncommited changes
5‐ the database is now in recoverd state
recovery in noarchivelog mode
1‐ restore all datafiles even one of them needs recovery
2‐ shutdown the instance
3‐ perform cancel based recovery
4‐ open database with resetlogs
SQL> shutdown immediate
!cp ‘...’ ‘...’
recover database until cancel using backup control file
cancel
alter database open resetlogs
recovery in archivelog mode
1‐ query the v$recover_file, v$archived_log, v$recovery_log
2‐ recover database
//mounted database
3‐ recover datafile ‘...’
//mounted database
4‐ recover tablespaceusers
//open database
5‐ recover datafile ‘...’
//open database
SQL> shutdown abort
Startup mount
Recover database
//recover datafile ‘...’
Alter database open
!cp ‘...’ ‘...’
alter database rename file ‘...’ to ‘...’
startup mount
alter database datafile ‘...’ offline
alter database open
restoredatafile
alter database rename file ‘...’ to ‘...’
alter database recover
recoverdatafile ‘...’
//recover tablespace<tablespace name>
alter database datafile ‘...’ online;
altertablespaceuser_data offline immediate;
alter database create datafile ‘...’ [as] ‘...’;
alter database recover;
altertablespacetable_data online;

5. AnarGodjaev
createcontrolfile;
recover database using backup controlfile;
1‐ shutdown and backup the database
2‐ restore all datafiles, dont restore controlfile, redo logs, password file and parameter file
3‐ mount database
4‐ recover datafiles
5‐ open database with resetlogs
6‐ perform a closed database backup
SQL> Recover database until cancel
Recover [automatic] database until time ‘2013‐10‐26:14:22:03’
Time based database recovery
1‐ shutdown and backup the database
2‐ restore all datafiles
//may need to recover archivelogs
3‐ mount database
4‐ recover database until time
5‐ open with resetlogs
6‐ backup the database
cancel based database recovery
1‐ redo logs are not multiplexed
one of the redo logs is missing
the missing redo log is not archived
2‐ shutdown database
3‐ restore all datafiles from backup
4‐ mount the database
5‐ recover database until cancel
6‐ open database with resetlogs
7‐ backup database
loss of current redo log files
- attempt to open database
- find the current log sequence number
- recover database until cancel
- drop and recreate log files if necessary
- open database with resetlogs
- perform whole database backup
//select * from v$log
SQL> alter database clear unarchivedlogfile group 2;