Thomas E' Canty ServerCare, Inc' Session

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Thomas E. CantyServerCare, Inc.Session 126
Data Guard Best Practices Tuning
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Speaker Qualifications

• Thomas E. Canty, Senior Oracle DBA, ServerCare,
  Inc.
• 19 years of Oracle experience, starting with
  version 5
• Has presented at IOUG, OpenWorld, NoCOUG, IASA,
• Has been a DBA, Developer, Architect, and IT
  Manager

• Has worked with Fortune 100 companies in
  Healthcare, Technology, Pharmaceuticals, and
  Telecom, as well as Major Universities

888-918-6309 http//www.ServerCare.com
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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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Data Guard Modes

• Maximum Performance Mode
• Least performance impact
• Default mode
• Maximum Protection Mode
• Emphasis on data safety
• Requires at least one secondary
• Maximum Availability Mode
• Emphasis on uptime
• Continues if secondary unavailable

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Physical vs. Logical Standby
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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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Session Data Unit (SDU)

• In Oracle Net connect descriptor
• sales.servercare.com
• (DESCRIPTION
• (SDU32767)
• (ADDRESS(PROTOCOLtcp)
• (HOSTsales-server)(PORT1521))
• (CONNECT_DATA
• (SIDsales.servercare.com)))
• Globally in sqlnet.ora
• DEFAULT_SDU_SIZE32767

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Session Data Unit (SDU) (Cont.)

• On standby DB, set in listener.ora
• SID_LIST_listener_name
• (SID_LIST
• (SID_DESC
• (SDU32767)
• (GLOBAL_DBNAMEsales.servercare.com)
• (SID_NAMEsales)
• (ORACLE_HOME/u01/app/oracle/product/10.2.0/db_1))
  )

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TCP Socket Buffer Size

• Set TCP socket buffer size 3 BDP
• Data Guard broker config. Set in sqlnet.ora
• Non Data Guard broker set in connect descriptor
• BDP - Bandwidth Delay Product
• RTT- Round Trip Time

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TCP Socket Buffer Size

• Assume gigabit network with RTT 25 ms
• BDP 1,000 Mbps 25msec (.025 sec)
• 1,000,000,000 .025
• 25,000,000 Megabits / 8 3,125,000 bytes
• In this example
• socket buffer size 3 bandwidth delay
• 3,125,000 3
• 9,375,000 bytes
• sqlnet.ora
• RECV_BUF_SIZE9375000
• SEND_BUF_SIZE9375000

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Network Queue Sizes

• Between kernel net. subsystems NIC driver
• txqueuelen - transmit queue size
• netdev_max_backlog - receive queue size
• Assumes gigabit network with 100ms latency
• Set queues
• ifconfig eth0 txqueuelen 10000
• sysctl.conf
• net.core.netdev_max_backlog20000

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Overall Network

• Ensure sufficient bandwidth to standby
• Verify TCP_NODELAY set to YES (default)
• RHEL3 - increase /proc/sys/fs/aio-max-size on
  standby
• From 131072(default) to 1048576
• Set RECV_BUF_SIZE SEND_BUF_SIZE 3 Bandwidth
  Delay Product (BDP)
• Use Session Data Unit (SDU) size of 32767
• Increase send receive queue sizes
• TXQUEUELENGTH
• NET_DEV_MAX_BACKLOG

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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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ARCn Redo Transport
1) Read from local arch 2) Receive redo 3) Ack -
know -ledge
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ASYNC LGWR Redo Transport
1) Write local redo 2) ASYNC send redo 3) Receive
redo 4) Ack - know -ledge 5) Write stdby redo
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SYNC LGWR Redo Transport
1) Write local redo 2) SYNC send redo 3) Receive
redo 4) Ack - know -ledge 5) Post receipt to LGWR
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Optimize ARCn Transport

• Increase MAX_CONNECTIONS to 5 on standby (if
  possible)
• default (2), maximum (5)
• Increase LOG_ARCHIVE_MAX_PROCESSES
• Larger than MAX_CONNECTIONS
• Up to network bandwidth
• default (2), maximum (30)

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Optimize LGWR Transport

• Decrease NET_TIMEOUT (default 180 secs.)
• Be careful! - Not too low
• New COMMITS
• COMMIT IMMEDIATE WAIT (default)
• COMMIT NOWAIT
• COMMIT NOWAIT BATCH

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All Redo Transport

• Standby redo logs
• Use fastest disks
• No RAID5
• Dont multiplex
• Use the recommended number of SRLs
• (maximum of online logfiles 1) maximum of
  threads

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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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Checkpoint Phase

• Checkpoint occurs
• During log switch
• LOG_CHECK_TIMEOUT expiration
• LOG_CHECKOUT_INTERVAL reached
• Reduce log switch interval
• Resize redo log to 1GB - primary and secondary
• Recommended - checkpoint every 15 minutes

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Checkpoint Phase (Cont.)

• Determine checkpoint frequency
• COL NAME FOR A35
• SELECT NAME, VALUE, TO_CHAR(SYSDATE, HHMISS)
  TIME
• FROM VSYSSTAT WHERE NAME 'DBWR checkpoints'
• NAME VALUE
  TIME
• ----------------------------------- ----------
  --------
• DBWR checkpoints 264
  081543
• SQLgt /
• NAME VALUE
  TIME
• ----------------------------------- ----------
  --------
• DBWR checkpoints 267
  083406

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Redo Read (Secondary)

• Obtain read rate for the standby redo log
• SQLgt ALTER SYSTEM DUMP LOGFILE
  '/u01/oradata/docprd/sredo01.log validate
• System altered.
• vi docprd_ora_3560.trc
• Mon Mar 12 085952 2007
• ----- Redo read statistics for thread 1 -----
• Read rate (ASYNC) 4527Kb in 0.58s gt 6.90
  Mb/sec
• Longest record 19Kb, moves 0/7586 (0)
• Change moves 4340/18026 (24), moved 2Mb
• Longest LWN 92Kb, moves 1/1365 (0), moved
  0Mb
• Last redo scn 0x0000.01272351 (19342161)

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Redo Apply (Secondary)

• Goal
• Redo apply rate (secondary) gt Redo create rate
  (primary)
• Carefully consider enabling DB_BLOCK_CHECKING
• LOW, MEDIUM and FULL options
• Possible performance impact

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Redo Apply (Cont.)

• Determine Log Block Size (LEBSZ)
• SELECT LEBSZ FROM XKCCLE WHERE ROWNUM1
• Get recovery blocks - at least two snapshots
• Managed Recovery Case
• SELECT PROCESS, SEQUENCE, THREAD, block,
  BLOCKS,
• TO_CHAR(SYSDATE, 'DD-MON-YYYY HHMISS') time
• from vMANAGED_STANDBY WHERE PROCESS'MRP0'
• Determine the recovery rate (MB/sec) for a
  specific archive sequence number
• Managed Recovery Case
• ((BLOCK_END - BLOCK_BEG) LOG_BLOCK_SIZE) /
• (TIME_END - TIME_BEG) 1024 1024

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Redo Apply (Cont.)

• Oracle Recommends

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Recovery

• Parallel Recovery (before 10.1.0.5)
• Set to number of CPUs
• recover managed standby database parallel ltgt
• PARALLEL_EXECUTION_MESSAGE_SIZE
• Can increase to 4096 or 8192
• Uses additional shared pool memory
• Problems if set too high
• DB_CACHE_SIZE
• Can set secondary DB_CACHE_SIZE gt primary
• Must set to primary before changing roles

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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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Arch Wait Events - Primary

• ARCH wait on ATTACH
• Time for all arch processes to spawn RFS
  connection
• ARCH wait on SENDREQ
• Time for all arch processes to write received
  redo to disk open close remote archived redo
  logs
• ARCH wait on DETACH
• Time for all arch processes to delete RFS
  connection

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LGWR SYNC Wait Events - Primary

• LGWR wait on ATTACH
• Time for all log writer processes to spawn RFS
  connection
• LGWR wait on SENDREQ
• Time for all log writer processes to write
  received redo to disk open close the remote
  archived redo logs
• LGWR wait on DETACH
• Time for all log writer processes to delete RFS
  conn.

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LGWR ASYNC Wait Events - Primary

• LNS wait on ATTACH
• Time for all network servers to spawn RFS
  connection
• LNS wait on SENDREQ
• Time for all network servers to write received
  redo to disk open close the remote archived
  redo logs
• LNS wait on DETACH
• Time for all network servers to delete RFS conn.
• LGWR wait on full LNS buffer
• Time for log writer (LGWR) process awaiting for
  network server (LNS) to free ASYNC buffer space

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Wait Events on Secondary

• RFS Write
• Time to write to standby redo log or archive log
  non I/O work like redo block checksum
  validation
• RFS Random I/O
• Time to write to a standby redo log to occur
• RFS Sequential I/O
• Time to write to an archive log to occur

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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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10g R2 Improvements

• Multiple archive processes can transmit a redo
  log in parallel to the standby database
• MAX_CONNECTIONS attribute of the
  LOG_ARCHIVE_DEST_n controls the number of these
  processes
• Parallel Recovery for Redo apply is automatically
  set equal to number of CPUs
• 10.1.0.5 and 10.2.0.1
• Fast-Start Failover
• Automatically fails over to a previously chosen
  physical standby database

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10g R2 Improvements (Cont.)

• LGWR ASYNC
• Uses a new process (LNSn) to transmit the redo
  data directly from the online redo log to the
  standby database
• Physical standby database flashback
• Can flash back temporarily for reporting
• Logical standby database
• Automatically deletes applied archived log
• RMAN
• Automatically creates temp datafiles after
  recovery

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11g Improvements

• Physical standby database open read/write for
  test or other purposes with zero compromise in
  data protection using new Snapshot Standby
• Automatic failover configurable for immediate
  response to designated events or errors
• More flexibility in primary/standby
  configurations
• e.g. Windows primary and Linux standby
• Rolling upgrade options now in physical standby
  with Transient Logical Standby
• ASYNC transport enhanced to eliminate the impact
  of latency on network throughput

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11g Improvements (Cont.)

• Fast detection of corruptions caused by lost
  writes in the storage layer
• SQL Apply supports XML data type (CLOB)
• Many performance, manageability, and security
  enhancements
• Support for new Oracle Database 11g Options
  Oracle Active Data Guard and Oracle Advanced
  Compression
• Fast Start Failover now available for Maximum
  Performance mode

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Outline

• Overview
• Network Optimization
• ARCn LGWR Redo Transport
• Checkpoint, Redo Read/Apply Recovery
• Wait Events
• 10g R2 11g Improvements
• Best Practices

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Best Practices

• Geographically separate primary standby DB
• Ensure standby hardware configuration same as the
  primary
• Tune standby for write intensive operations
• Test Data Guard before deploy in production
• Set standard OS and DB parameters to recommended
  values
• Perform switchover testing
• Fully document a failover procedure
• Use FORCE LOGGING mode

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Best Practices (Cont.)

• Use real-time apply
• Use the Data Guard Broker
• Enable Flashback Database on both primary and
  secondary databases
• Evaluate using AFFIRM attribute
• Possible performance issues on primary
• Verify Asynchronous I/O enabled
• Carefully consider DB_BLOCK_CHECKING

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Best Practices (Cont.)

• Dont multiplex standby redo logs (SRLs)
• Correctly set number of SRLs
• Increase PARALLEL_EXECUTION_MESSAGE_SIZE
• Place SRLs in fast disk group or disks
• Use at lease two standby DBs with Maximum
  Protection Mode
• Utilize COMMIT NOWAIT if appropriate

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Best Practices (Cont.)

• Ensure appropriate bandwidth between primary and
  secondary
• Increase default send receive queue sizes
• TXQUEUELENGTH
• NET_DEV_MAX_BACKLOG
• Session Data Unit
• Adjust value to 32767
• Improvement during large data transmissions

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Questions?

• Lots of things we didnt cover
• If we dont cover something you wanted to hear,
  please contact me.

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Session 126 Data Guard Best Practices Tuning
THANK YOU!
Please fill out evaluations!
Email Tom Canty tom.canty_at_servercare.com
Or Call 888-918-6309 http//www.ServerCare.com