DBAII_R1_1_Les07_E

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Instance and Media Recovery Structures : 

Instance and Media Recovery Structures

Objectives : 

Objectives After completing this lesson, you should be able to do the following: Describe the Oracle processes, memory structures, and files relating to recovery Identify the importance of checkpoints, redo log files, and archived log files Describe ways to tune instance recovery

Overview : 

Overview Database Datafile 1 Datafile 2 Datafile 3 Controlfile Redo log file 1 Instance SGA Redo log buffer Databasebuffer cache Large Pool Java Pool Shared pool Data dict.cache Shared SQLand PL/SQL ARCn Userprocess Serverprocess PGA Parameterfile Passwordfile Archivedlog files

Large Pool : 

Large Pool Can be configured as a separate memory area in the SGA to be used for: Oracle backup and restore operations I/O server processes Session memory for the shared servers Is sized by the LARGE_POOL_SIZE parameter

Database Buffer Cache, DBWn, and Datafiles : 

Database Buffer Cache, DBWn, and Datafiles Instance SGA Database buffer cache Large pool Java pool Shared pool Data dict.cache Shared SQLand PL/SQL ARCn Userprocess Serverprocess PGA Database Datafile 1 Datafile 2 Datafile 3 Controlfile Redo log file 1 Redo log file 2 Parameterfile Passwordfile Archived log files PMON DBW0 SMON LGWR CKPT DBW1 Redo log buffer

Redo Log Buffer, LGWR, and Redo Log Files : 

Redo Log Buffer, LGWR, and Redo Log Files Instance SGA Database buffer cache Large pool Java pool Shared pool Data dict.cache Shared SQLand PL/SQL ARCn Userprocess Serverprocess PGA Database Datafile 1 Datafile 2 Datafile 3 Controlfile Redo log file 1 Redo log file 2 Parameterfile Passwordfile Archived log files PMON SMON LGWR CKPT Redo log buffer DBWn

Multiplexed Redo Log Files : 

Group 1 log1a.rdo log1b.rdo Group 2 log2a.rdo log2b.rdo Group 3 Multiplexed Redo Log Files Disk 1(Member a) Disk 2(Member b) log3a.rdo log3b.rdo

Redo Log Files in Enterprise Manager : 

Redo Log Files in Enterprise Manager

Checkpointing : 

Checkpointing Checkpoints are used to determine where recovery should start. Checkpoint position – where recovery starts Checkpoint queue – link list of dirty blocks

Types of Checkpoints : 

Types of Checkpoints Full checkpoint All dirty buffers are written SHUTDOWN NORMAL, IMMEDIATE, or TRANSACTIONAL ALTER SYSTEM CHECKPOINT Incremental checkpoint (Fast-Start checkpoint) Periodic writes Only write the oldest blocks Partial checkpoint Dirty buffers belonging to the tablespace ALTER TABLESPACE BEGIN BACKUP ALTER TABLESPACE tablespace OFFLINE NORMAL

CKPT Process : 

CKPT Process Instance SGA Database buffer cache Large pool Java pool Shared pool Data dict.cache Shared SQLand PL/SQL ARCn Userprocess Serverprocess PGA Database Datafile 1 Datafile 2 Datafile 3 Controlfile Redo log file 1 Redo log file 2 Parameterfile Passwordfile Archived log files PMON SMON LGWR CKPT Redo log buffer DBWn

Multiplexed Control Files : 

Multiplexed Control Files Instance SGA Database buffer cache Large pool Java pool Shared pool Data dict.cache Shared SQLand PL/SQL ARCn Userprocess Serverprocess PGA Database Datafile 1 Datafile 2 Datafile 3 Redo log file 1 Redo log file 2 Parameterfile Passwordfile Archived log files PMON DBWn SMON LGWR CKPT Controlfiles Redo log buffer

Control Files in Enterprise Manager : 

Control Files in Enterprise Manager

ARCn Process and Archived Log Files : 

ARCn Process and Archived Log Files Instance SGA Database buffer cache Large pool Java pool Shared pool Data dict.cache Shared SQLand PL/SQL ARC0 Userprocess Serverprocess PGA Database Datafile 1 Datafile 2 Datafile 3 Controlfile Redo log file 1 Passwordfile Archived log filesdest 1 Parameterfile Passwordfile Archived log filesdest 2 ARC1 Redo log buffer

Database Synchronization : 

Database Synchronization All datafiles (except offline and read-only) must be synchronized for the database to open. Synchronization is based on the current checkpoint number. Applying changes recorded in the redo log files synchronizes datafiles. Redo log files are automatically requested by the Oracle server.

Phases for Instance Recovery : 

Database Datafile 1 UndoDatafile Datafile 3 Controlfile Redo log file 1 Redo log file 2 146.5 146.5 146.5 146.5 146.5 145 Phases for Instance Recovery 1. Datafiles out-of-synch 2. Roll forward (redo) 3. Committed and non- committed data in files 4. Roll back (undo) 5. Committed data in files SQL*Plus Serverprocess PGA Undo Checkpoint Instance SGA Redo log buffer Database buffer cache Large pool Java pool Shared pool Data dict.cache Shared SQLand PL/SQL ARCn

Tuning Crash and Instance Recovery Performance : 

Tuning Crash and Instance Recovery Performance Tuning the duration of instance and crash recovery Tuning the phases of instance recovery

Tuning the Duration of Instance and Crash Recovery : 

Tuning the Duration of Instance and Crash Recovery Methods to keep the duration of instance and crash recovery within user-specified bounds: Set initialization parameters to influence the number of redo log records and data blocks involved in recovery. Size the redo log file to influence checkpointing frequency. Issue SQL statements to initiate checkpoints. Parallelize instance recovery operations.

Initialization Parameters Influencing Checkpoints : 

Initialization Parameters Influencing Checkpoints Parameter FAST_START_MTTR_TARGET LOG_CHECKPOINT_TIMEOUT LOG_CHECKPOINT_INTERVAL Definition Expected MTTR specified in seconds Amount of time that has passed since the incremental checkpoint at the position where the last write to the redo log occurred Number of redo log file blocks that can exist between an incremental checkpoint and the last block written to the redo log

Controlling Instance Crash Recovery Time : 

Controlling Instance Crash Recovery Time

V$INSTANCE_RECOVERY : 

V$INSTANCE_RECOVERY Used to monitor the mechanisms available to limit recovery I/O Statistics from this view to calculate which parameter has the greatest influence on checkpointing.

Tuning the Phases of Crash and Instance Recovery : 

Tuning the Phases of Crash and Instance Recovery Tuning the roll forward phase Tuning the rollback phase

Tuning the Rolling Forward Phase : 

Tuning the Rolling Forward Phase Parallel block recovery RECOVERY_PARALLELISM specifies the number of concurrent recovery processes

Tuning the Rolling Back Phase : 

Tuning the Rolling Back Phase Fast-start on-demand rollback Fast-start parallel rollback

Fast-Start On-Demand Rollback : 

Fast-Start On-Demand Rollback Server process encountering data to be rolled back performs the following: Rolls back the block containing the required row Hands off further recovery, which may be in parallel, to SMON Improvedresponse

Fast-Start Parallel Rollback : 

Fast-Start Parallel Rollback SMON Undosegment P001 P000 P002 P003

Controlling Fast-Start Parallel Rollback : 

Controlling Fast-Start Parallel Rollback FAST_START_PARALLEL_ROLLBACK parameter

Monitoring Parallel Rollback : 

Monitoring Parallel Rollback V$FAST_START_SERVERS V$FAST_START_TRANSACTIONS

Summary : 

Summary In this lesson, you should have learned how to: Identify components of the instance and database that are significant to recovery Tune crash and instance recovery

Practice 7 Overview : 

Practice 7 Overview This practice covers the following topics: Querying dynamic performance views to determine the current state and structure of the database Explaining the use of specific initialization parameters Mirroring of the control files and redo log files

Slide 43: 

Practice 7

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