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Chapter 16 Tuning RMAN. Background. One of the hardest chapters to develop material for Tuning RMAN can sometimes be difficult Authors tried to capture repeatable techniques for performance tuning. Why Tune RMAN. Backups taking too long

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Chapter 16 Tuning RMAN

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  • One of the hardest chapters to develop material for
  • Tuning RMAN can sometimes be difficult
  • Authors tried to capture repeatable techniques for performance tuning
why tune rman
Why Tune RMAN
  • Backups taking too long
  • Performance of the system is impacted during RMAN backups
  • Restore and recovery time too long, downtime causes the business to lose money
one approach to tuning
One Approach to Tuning...

1. Identify measurable business performance requirements.

2. Collect data and measure performance.

3. Identify bottlenecks.

4. Make adjustments that will alleviate the worst bottleneck.

5. Repeat steps 1–4 until your performance goals are achieved.

systemic influences
Systemic Influences
  • CPU
  • Memory
  • Operating system
  • Disk layout
  • Network
  • Database architecture
  • Tape technology and vendor
  • Application design
  • Design of data model and its physical implementation
  • Robustness of SQL statements
views used for monitoring
Views Used for Monitoring
identifying rman processes
Identifying RMAN Processes
  • Sometimes you might want to kill an RMAN process

SQL> SELECT b.sid, b.serial#, a.spid, b.client_info

FROM v$process a, v$session b

WHERE a.addr = b.paddr

AND b.client_info LIKE '%rman%';

measuring backup performance
Measuring Backup Performance
  • If you can’t measure it, you can’t manage it...

SQL> SELECT session_recid, input_bytes_per_sec_display,


time_taken_display, end_time

FROM v$rman_backup_job_details

ORDER BY end_time;

monitoring rman job progress
Monitoring RMAN Job Progress
  • Are we there yet? Are we there yet?

SQL> select sid, serial#, sofar, totalwork, opname,

round(sofar/totalwork*100,2) "% Complete"

from v$session_longops

where opname LIKE 'RMAN%'

and opname NOT LIKE '%aggregate%'

and totalwork != 0

and sofar <> totalwork;

identifying i o bottlenecks
Identifying I/O Bottlenecks
  • How do you determine I/O is a bottleneck?
  • Asynchronous I/O vs. synchronous

SQL> SELECT sid, serial, filename, type, elapsed_time, effective_bytes_per_second

FROM v$backup_async_io

WHERE close_time > sysdate – 7;

improving tape i o performance
Improving Tape I/O Performance
  • RMAN can be configured to backup directly to tape (see MML chapter)
  • Tape I/O is often the bottleneck
  • Can be difficult to diagnose and resolve
  • Use an incremental backup strategy with block change tracking
  • Adjust multiplexing of backup sets
improving tape i o performance12
Improving Tape I/O Performance
  • Many variables to consider...
  • MML software configuration
  • Network configuration
  • Level of tape compression
  • Tape streaming
  • Tape block size
maximizing throughput to backup device
Maximizing Throughput to Backup Device
  • Multiplexing with RMAN means it can read multiple files at the same time and simultaneously write them to the same backup piece
  • As of Oracle 10g, RMAN will automatically tune the level of multiplexing
maximizing throughput to backup device14
Maximizing Throughput to Backup Device
  • Filesperset limits the number of files in each backup set
  • Maxopenfiles limits the number of files simultaneously open
  • Diskratio instructs RMAN to read datafiles from a specified number of disks
setting large pool memory size
Setting Large Pool Memory Size
  • One approach, use ASMM

1. Ensure statistics_level is set to TYPICAL (the default) or ALL

2. Set sga_target to an appropriate nonzero value for your database not exceeding the sga_max_size

3. Set the following initialization parameters to zero:

    • shared_pool_size
    • large_pool_size
    • java_pool_size
    • db_cache_size
    • streams_pool_size
tuning media recovery
Tuning Media Recovery
  • With Oracle 10g or higher, RMAN should automatically perform recovery in parallel
  • You can override the default behavior:

RMAN> recover database parallel 4;

tuning crash recovery
Tuning Crash Recovery
  • Crash recovery is performed by SMON after a database crash (power outage, shutdown abort)
  • Why would you care how long crash recovery takes?
  • Can be tuned with fast_start_mttr_target
  • Gives the database a target time for performing crash recovery
one approach to tuning crash recovery
One Approach to Tuning Crash Recovery

1. Disable the initialization parameters that interfere with fast_start_mttr_target

2. Determine the lower bound for fast_start_mttr_target

3. Determine the upper bound for fast_start_mttr_target

4. Select a value within the upper and lower bounds

5. Monitor and adjust

slowing rman down
Slowing RMAN Down
  • Sometimes RMAN can impact other processes running on the system
  • Couple of techniques:
    • The backup duration ... minimize load command
    • The rate clause of the allocate channel or configure channel command
improving performance through parallelism
Improving Performance Through Parallelism
  • Use the parallel clause of the configure command
  • Doesn’t do much for single disk systems

RMAN> configure device type

disk parallelism 4;

RMAN> show channel;

improving performance using incremental features
Improving Performance Using Incremental Features
  • RMAN has many incremental features
  • Incremental backups
  • Change tracking
  • Incremental update