- DBGuide.net · 2010-03-30 · Viewing AWR Report AWR Report displays all statistics captured over a snapshot range Roughly equivalent to the STATSPACK

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AWR 이용한 Detailed Analysis

Jun Kim

System Analyst

Solution Support Center

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Agenda

• Do You Know What is normal at your site

• AWR 이란 ?

• Statistics Stored In AWR

• Viewing AWR Report

• Thinking About Queue

• AWR 이용한 분석 및 모니터링

• Oracle ACS 진단 Service

• Q & A

• Appendix

Do U Know What is normal at your site?

Get an accurate description of the problem

Check the OS for exhausted resources

Gather database statistics

Check for the most common pitfalls

Analyze the data gathered, focus on wait events, theorize the cause of the problem

Propose a series of remedial actions, then implement them

Measure the effect of the changes

Repeat any steps, as required, until performance goals met


Get an accurate description of the problem

The scope of problem

Instance wide or local to a user / group of users or a program.

The expected response time or throughput

The response time is getting slower or throughput decreased.

The Time frame

When does the problem occur?

Any recent changes

Data volume increases, New optimizer statistics or application

modification, SW/HW upgrades


Check the OS for exhausted resources

CPU Utilization

CPU utilization / Load average ( Run queue )

Memory Utilization

Page out ( Swap out ) / SR ( scan ratio )

Network Socket overflow

Socket overflow / Drop Packets, Fragments

Top Processes

Top Processes have consumed lots of CPU

CPU Utilization ( User 100% ) , it need more CPU or sub-optimal SQL ….?


Gather database statistics

Indicate the primary bottleneck

Find primary bottleneck in database.

STATSPACK / AWR

STATSPACK ( 9i ) / AWR ( 10g ~~~)

Third Party tool

Third Party productions

scripts

Using Oracle dictionary view as you needed (dbmon.sql)


Check for most common pitfalls

Bad connection management

Bad use of cursors and shared pool

Use bind variable ( avoid hard parsing )

Redo log setup problems

Checkpoint ( IO related ) / Archive problem

Serialization of data blocks in data buffers

Application design / Heavy insert / block parameter…

Long full table scan

Missing Index / sub-optimal SQL Plan

In disk sorting

High amount of recursive SQL

Space management

Schema errors / Optimizer problems

Use of nonstandard initialization parameters


Analyze data gathered

Find pattern

Building Conceptual model

Identify bottleneck

Top 5 wait events

Load profile

Instance Efficiency

Check OS resources as you need

Top processes have used lots of CPU

Top CPU SQL

Top IO SQL


Propose a series of remedial actions, implement them

Change one thing one time

Do not overlap when multiple changes are applied

Measure the effect of the changes

Re-examine the statistics

Implement changes affect the performance ( good or bad )

Iteration

Until performance goal met

AWR(Automatic Workload Repository) 이란 ?

Automatically collects & persists database instance statistics

How to enable / disable & How to persist the data.

STATSPACK++

Cumulative value

Default in 10G

Database Load + Resources ( internal + external )

Stored in SYSAUX

SYSAUX TABLESPACE 크기 산정

Provides in DBA_HIST_* View

View sample

Statistics Stored In AWR

Counter Statistics

Ex “session logical reads”

Value Statistics

Ex “logons currents”

Time Statistics

Ex “DB time”

Metric

Ex “DB Block gets Per Txn”

Sampled

Ex “ASH ( Active Session History )”

Viewing AWR Report

AWR Report displays all statistics captured over a snapshot

range

Roughly equivalent to the STATSPACK report

Available EM

Manual Creation through SQL*Plus

awrrpt.sql

awrddrpt.sql comparison two snapshots periods

ashrpt.sql Detailed analysis of ASH data over small periods of time

awrsqrpt.sql Detailed SQL Report

Think About Queue

• Queuing 이론이란…..? 롯데리아에서 햄버거를 하나 주문 함에 있어 주문을 하기 전 기다리는 시간과 주문을

하여 햄버거를 받는 시간을 생각해 보자.

컴퓨터 시스템도 cpu를 할당 받아 일하는 시간과 cpu를 할당 받기 위해 기다리는 시간이있다.

롯데리아와 다른점은 기다리는 줄이 하나라는 점이다.

• Rt(Response Time) = Qt(Queuing Time) + St ( Service Time) 햄버가 하나 주문하는데 걸린 시간은 줄서 있는 시간 + 주문하여 받은 시간이다.

시스템의 응답시간도 위와 마찬가지 모델로 이루어져 있다.

Queue

Server 1

Server 2

Server3

Server4Job1 Job 2 Job 3 Job N

workload = job = load profile

CPU = Server

AWR Report Header

DB Name DB Id Instance Inst num Release RAC Host

PROD 3347383166 PROD1 1 10.2.0.3.0 YES Hostname

Snap Id Snap Time Sessions Cursors/Session

Begin Snap: 26885 06-Apr-09 07:30:10 1721 172.2

End Snap: 26907 06-Apr-09 18:30:01 6416 166.9

Elapsed: 659.86 (mins)

DB Time: 43,790.57 (mins)

해당 SNAP구간에서 DB Server 에 대한 건강 검진을 받아 보자

Operating System Statistics

Statistic TotalAVG_BUSY_TIME 0

AVG_IDLE_TIME 0

AVG_IOWAIT_TIME 907,133

AVG_SYS_TIME 3,049,915

AVG_USER_TIME 581,501

BUSY_TIME 249,064

IDLE_TIME 656,704

IOWAIT_TIME 114,461,748

SYS_TIME 384,451,747

USER_TIME 73,432,519

LOAD 31,548,446

OS_CPU_WAIT_TIME 82,913,302

RSRC_MGR_CPU_WAIT_

TIME0

VM_IN_BYTES 104,440,000

VM_OUT_BYTES 0

PHYSICAL_MEMORY_BY

TES###############

NUM_CPUS 126

NUM_CPU_SOCKETS 63

Operating System Statistics

시스템 CPU 사용에 대해 해당 snap 구간 및 추이를 확인 하여 특이사항 여부 를 판단해야 함.

CPU Usage (%) - LGEGERPIF1Q

0%

10%

20%

30%

40%

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100%

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Date & Time

%idle

%w io

%sys

%usr

CPU는 혼자 움직이는 것이 아님. 손님이 없는 식당의 종업은 항상 idle상태 ,혹은 serving이 아닌다른 일을 함 (ex:주방일… )

손님이 들어와 serving을 시작 하는 것과 같이 CPU User time을증가시키는 workload가 있음. 해당 workload는 무엇인가 ?

CPU 추이를 일단위 , 일주일 더는 월단위로 파악하여 추세를알 수 있도록 함.

( 식당 종업원의 효율 및 고용 증가 및 감소 자료 활용)

CPU Usage (%)

Load Profile

Per Second Per TransactionRedo size: 2,979,473.47 2,979,473.47

Logical reads: 20,190.94 20,190.94

Block changes: 954,506.71 954,506.71

Physical reads: 6,468.39 6,468.39

Physical writes: 17,533.29 17,533.29

User calls: 118.82 118.82

Parses: 17,519.53 17,519.53

Hard parses: 118.72 118.72

Sorts: 999.93 999.93

Logons: 6.78 6.78

Executes: 4,604.07 4,604.07

Transactions: 31.2 31.2

Load Profile

위 load profile을 보고 해당 DB Server의 load를 말 할 수 있는가 ?

현재 Load profile을 확인 하고 load에 대한 서버의 영향 도를 말 할 수 있는가 ?

Let’s Talk

DB의 STAT 은 DB Server에서 일어나는 여러가지 job으로 해석할 수 있으며, 특히 load profile의stat은 DB Server내의 주된 workload로 이에 대한 trend 파악이 필요함. dba_hist_sysstat view참조.

CPU에 일을 시키는 여러 가지 작업임.

해당 load 파일을 통해 주어진 시간의workload를 파악 할 수 있음

어떤 workload를 통해 서버가 busy하게되는지를 파악할 수 있음.

예를 들어 커피숍에서 점심시간 동안바쁘게 일을 했다면 , 그 시간 동안에커피를 몇잔, 주스를 몇잔 혹은 홍차를몇잔 아니면 음식재료를 준비하면서시간을 소비했는지를 알 수 있음.이를 통해 다른 날 보다 어떤 품목이 많이팔렸는지를 알 수 있음.(특이 사항 검증 )

Global Cache Load Profile

Per Second Per Transaction

Global Cache blocks received: 5,883.06 33.39

Global Cache blocks served: 7,278.89 41.31

GCS/GES messages received: 69,624.98 395.12

GCS/GES messages sent: 49,963.55 283.54

DBWR Fusion writes: 101.46 0.58

Estd Interconnect traffic (KB) 128,652.73

Global Cache Load Profile

위 지표들은 노드간의 주고 받은 일의 양을 나타내는 지표로 이들 Job에 따른 성능의 영향에 대해확인이 필요함. workload Characteristics 참조

interconnect traffic 양이 증가 한다며 , 우선적으로 cluster wait이 높은 SQL을 참조 할 필요가 있음.

CR FLOW DIAGRAM

앞에서 보았던 일반 load지표와 별도로RAC에서의 load지표임.

예를 들어 커피숍에서 일하는 직원이혼자가 아닌 둘 이상이라면 커피 주문에대해 주문을 받고 , 커피를 만들고 하면서두 직원 사이에 주고 받는 메시지 며,커피잔 등…두사람 사이에 일어나는동작에 대한 지표라 생각 할 수 있다.

오라클에서 LMS 프로세스가 이런operation을 하는 대표적이 프로세스라할 수 있다.

Global Cache Efficiency Percentages

Buffer access - local cache %: 97.8

Buffer access - remote cache %: 0.64

Buffer access - disk %: 1.56

Avg global enqueue get time (ms): 0.6

Avg global cache cr block receive time (ms): 0.8

Avg global cache current block receive time (ms): 0.7

Avg global cache cr block build time (ms): 0

Avg global cache cr block send time (ms): 0

Global cache log flushes for cr blocks served %: 3.9

Avg global cache cr block flush time (ms): 2.9

Avg global cache current block pin time (ms): 0

Avg global cache current block send time (ms): 0

Global cache log flushes for current blocks served %: 0.3

Global Cache Efficiency Percentages

Global Cache and Enqueue Services - Workload Characteristics

구분 권고치

CR Block Received

Time12 이하

CURR Block Received

Time30 이하

Load Profile Logical Reads & OS Stat Example

Logical Reads

OS CPU 사항

Logical Reads (per sec)

0

200,000

400,000

600,000

800,000

1,000,000

1,200,000

1,400,000

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8:30

Date & Time

CPU Usage (%) - LGEGERPIF1Q

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

24 08

:00

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Date & Time

%idle

%w io

%sys

%usr

Logical Reads / Sec

CPU Usage (%)

Wait Class

Wait Class Waits%Time -

outs

Total Wait

Time (s)

Avg wait

(ms)Waits /txn

User I/O 221,611,868 0 1,478,813 7 37.93

Cluster 493,638,715 0.03 406,741 1 84.49

System I/O 24,842,756 0 36,841 1 4.25

Other 24,548,596 51.48 35,896 1 4.2

Application 1,445,321 3.64 26,966 19 0.25

Concurrency 147,553,001 0.05 23,523 0 25.26

Network 166,524,214 0 13,272 0 28.5

Commit 3,623,870 0 9,074 3 0.62

Configuration 805,549 76.55 1,065 1 0.14

커피 점원이 커피 주문을 받아 본인이 하는 일과 기계가 하는 일로 나누어 볼 수 있다. 점원이 커피를 기계에서 기다리는시간 동안이 wait 상태라 말 할 수 있음.

오라클은 RT = ST + WT 으로 정의를 하고 있으며,여러 가지 wait event를 9개의 category로 분류 하고 있음.

위 테이블을 통해 해당 snap 구간 중 어떤 wait class가 가장 많은 부분을 차지 하고 있음을 알 수 있음.

RT = ST + WT

Service Time은어떻게 ?

Top 5 Timed Events

Event Waits Time(s) Avg Wait(ms)% Total Call

TimeWait Class

CPU time 910,471 45.2

db file sequential read 55,208,969 690,127 13 34.2 User I/O

log file sync 7,241,625 100,931 14 5 Commit

gc current block 3-way 31,287,718 75,500 2 3.7 Cluster

gc current block 2-way 41,850,395 70,941 2 3.5 Cluster

Wait Class별이 아닌 개별 wait event로 snap 구간 중 가장 wait time이 높은 top 5 event임.

평사 시 top 5 event는 업무 형태가 변경이 되거나 추가 되지 않는 다면 크게 변동이 없을 확률이 높음.

top 5 event에 대해 평균 wait time에 대한 모니터링 및 평상시에 발생 하지 않은 event가 top 5 event로 올라 온다면해당 event에 대해 검증이 필요함.

예를 들어 과도하게 IO wait이 증가 하였다면 , AWR의 SQL Part의 high buffer gets / High disk read등을 통해 해당시간의 SQL을 검증을 통해 특이 사항 여부를 확인 해야 함. 또는 과도하게 librarycache 및 shared pool관련 wait이증가 하였다면 SGA의 Memory Part에서 해당 메모리의 증감 여부, invalidation여부 등을 확인 해야 함.

오라클은 많은 수의 wait event를 가지고 있으며 , 각 event에 대해서는 oracle manual을 참조.

db file sequential read

IO 성능 여부 검토

AWR 리포트의 Avg Wait(ms), “IO Stats” section에서 Av Rd (ms) 항목의수치가 다소 높게 나온다면 원인을 찾기 위해 O/S 및 Storage Level 에서의 IO

통계치를 살펴본다.

IO 부하를 많이 발생시키는 SQL문들을 튜닝한다.

AWR의 ‘SQL ordered by physical read‟를 검사하고, 튜닝을 실시한다.

충분한 튜닝을 하였음에도 불구하고 여전히 IO 시스템에 대한부하가 큰 경우는 주로 디스크 성능 자체의 bottleneck이거나파일이나 디스크에 대한 작업배분이 잘못 설정되었을 가능성검토

이와 같은 IO bandwidth 문제에 대한 정확한 증거로는 ‘db file parallel write‟,

„direct read‟, „direct write‟, 그리고 ‘log file parallel write‟ 등의 event가 Top-5

waits events에 나타나는 경우가 많다.

log file sync

Redo log

LGWR

redo

write down

commit1

2

shadow

On-line redo log

3

4commit 완료

log file sync란 ?

Shadow process가 commit을 요청 시 LGWR가해당 redo 를 online redo log file에 write한 후해당 메시지를 shadow process에게 전달하는event로 1 ~ 4번을 거쳐 완료 됨.

대표적인 log file sync 성능 저하 원인은…

IO Bottleneck

IPC 통신 ( ex : semaphore )

RAC 환경 하에서 SCN 동기화

등으로 해당 항목에 대해서 drill down해야 함.

Global Cache Wait Eventsgc current block 2-way

SGA1

SGA2

LGWRLGWR:

Log sync

Wait complete:gc current block 2-way

Wait:gc current request

Direct send

Block transfer

1

2

3

LMS

LMS

Global Cache Wait Eventsgc current block 3-way

SGA1

SGA2

LGWR

LMS

LMS

Wait complete:gc current block 3-way

Wait:gc current request

Direct

message

Block transfer

LMS

Resource

Master

1 2

3

4

SGA Breakdown

Pool Name Begin MB End MB % Diff

large free memory 221.68 221.55 -0.06

large PX msg pool 2.32 2.45 5.39

shared library cache 495.53 1,534.90 209.75

shared sql area 4,131.00 6,888.16 66.74

shared free memory 6,783.22 2,152.72 -68.26

SGA의 large pool 및 shared pool의 free memory & sql area 등 주요 항목에 대해 증감 여부를 확인 할 수 있음.

특정 메모리가 과도하게 증가하거나 감소 하였다면 해당 시점의 어떤 변화 가 있었는지를 load profile 및 wait event를통해 먼저 확인 후 drill down 해야 함.

메모리의 변동 사항 또한 CPU추이와 같이 하루 , 혹은 일주일 pattern을 모니터링 하는 것이 필요함.

Memory Statistics – library cache statistics

NamespaceGet

RequestsPct Miss Pin Requests Pct Miss Reloads

Invali-

dations

BODY 4,383,881 0.01 137,380,417 0 443 0

CLUSTER 995 0.4 1,438 0.56 4 0

INDEX 1,433,787 0.02 1,553,075 0.16 2,047 0

JAVA DATA 2,468 0 40 7.5 3 0

JAVA RESOURCE 189 0 567 0.35 2 0

PIPE 894,065 0.1 1,342,415 0.06 0 0

SQL AREA 299,644 97.391,458,251,177 0.12 233,980 12,122

TABLE/PROCEDURE 4,479,060 0.2 189,209,372 0.05 33,573 0

TRIGGER 105,057 0.08 5,933,235 0 129 0

SGA의 shared pool area중 library cache영역에 대한 데이터로 reloads 및 invalidation에 대해 모니터링이 필요함.

SQL Statistics

SQL Ordered by Elapsed Time

SQL Ordered by CPU Time

SQL Ordered by Gets

SQL Ordered by Reads

SQL Ordered by Executions

SQL Ordered by Parse Calls

SQL Ordered by Sharable Memory

SQL Ordered by Version Count

SQL Ordered by Cluster Wait Time

실제 OUPTPUT

..\��\LG��\��ϵ�\�� û��\awr �м��\awrrpt_1_2

TIME MODEL Statistics Hierarchy

DB TIME

• DB CPU

• Connection Management Elapsed Time

• Sequence Load Elapsed Time

• SQL Execute Elapsed Time

Repeated Binding Elapsed Time

• Parse Time Elapsed Time

Hard Parse Elapsed Time

Hard Parse (Sharing Criteria) Elapsed Time

Hard Parse Bind Mismatch Elapsed Time

Failed Parse Elapsed Time

Failed Parse (Out of Shared Memory)

• PL/SQL Execution Elapsed Time

• Inbound PL/SQL RPC Elapsed Time

• PL/SQL Compilation Elapsed Time

• Java Execution Elapsed Time

Time Model Statistics

Statistic Name Time (s) % of DB Time

sql execute elapsed time 2,206,102.92 97.5

DB CPU 672,296.64 29.71

PL/SQL execution elapsed time 248,800.73 11

parse time elapsed 64,204.13 2.84

connection management call elapsed time 60,816.54 2.69

repeated bind elapsed time 50,368.84 2.23

hard parse elapsed time 4,922.33 0.22

hard parse (sharing criteria) elapsed time 2,343.76 0.1

sequence load elapsed time 1,688.86 0.07

DB time 848.57 0.04

background elapsed time 616.18 0.03

background cpu time 343.6 0.02

Time Model Statistics

Oracle ACS 진단 Service

DCR ( Database Configuration Review )

DPI ( Database Performance Inspection )

PDI ( Periodic Database Inspection)

ORA ( Operation Readiness Assessment )

OSR ( Oracle System Review )

BPR (Backup & Recovery Review )

KNT ( Knowledge Transfer )

Q U E S T I O N S

A N S W E R S

<Insert Picture Here>Appendix

• Create & Drop & Modify Snapshot

• AUTOMATIC WORKLOAD REPOSITORY

• CR Flow Diagram

• DBA_HIST_SYSTAT

• STATISTICS

• Wait Events

Create & Drop & Modify snapshot

Create SnapshotBEGIN

DBMS_WORKLOAD_REPOSITORY.CREATE_SNAPSHOT ();

END;

/

Drop SnapshotBEGIN

DBMS_WORKLOAD_REPOSITORY.DROP_SNAPSHOT_RANGE (low_snap_id => 22,

high_snap_id => 32, dbid => 3310949047);

END;

/

Modify SnapshotBEGIN

DBMS_WORKLOAD_REPOSITORY.MODIFY_SNAPSHOT_SETTINGS( retention => 43200,

interval => 30, topnsql => 100, dbid => 3310949047);

END;

/

Automatic Workload RepositoryReport items

• Report Summary

• Wait Events Statistics

• SQL Statistics

• Instance Activity Statistics

• IO Stats

• Buffer Pool Statistics

• Advisory Statistics

• Wait Statistics

• Undo Statistics

• Latch Statistics

• Segment Statistics

• Dictionary Cache Statistics

• Library Cache Statistics

Main Report

• Memory Statistics

• Streams Statistics

• Resource Limit Statistics

• init.ora Parameters

Main Report

• RAC Report Summary

(RAC Statistics)

• Global Enqueue Statistics

• Global CR Served Stats

• Global CURRENT Served Stats

• Global Cache Transfer Stats

More RAC Statistics

Automatic Workload RepositoryMain Report

• Cache Sizes

• Load Profile

• Instance Efficiency Percentages (Target 100%)

• Shared Pool Statistics

• Top 5 Timed Events

Report Summary

• Global Cache Load Profile

• Global Cache Efficiency Percentages (Target

local+remote 100%)

• Global Cache and Enqueue Services - Workload

Characteristics

• Global Cache and Enqueue Services - Messaging

Statistics

RAC Report Summary


• Time Model Statistics

• Wait Class

• Wait Events

• Background Wait Events

• Operating System Statistics

• Service Statistics

• Service Wait Class Stats

Wait Events Statistics

• SQL ordered by Elapsed Time

• SQL ordered by CPU Time

• SQL ordered by Gets

• SQL ordered by Reads

• SQL ordered by Executions

• SQL ordered by Parse Calls

• SQL ordered by Sharable Memory

• SQL ordered by Version Count

• SQL ordered by Cluster Wait Time

• Complete List of SQL Text

SQL Statistics


• Instance Activity Stats

• Instance Activity Stats - Absolute Values

• Instance Activity Stats - Thread Activity

Instance Activity Statistics

• Instance Recovery Stats

• Buffer Pool Advisory

• PGA Aggr Summary

• PGA Aggr Target Stats

• PGA Aggr Target Histogram

• PGA Memory Advisory

• Shared Pool Advisory

• SGA Target Advisory

• Streams Pool Advisory

• Java Pool Advisory

Advisory Statistics

• Tablespace IO Stats

• File IO Stats

IO Stats

Buffer Pool Statistics


• Buffer Wait Statistics

• Enqueue Activity

Wait Statistics

• Segments by Logical Reads

• Segments by Physical Reads

• Segments by Row Lock Waits

• Segments by ITL Waits

• Segments by Buffer Busy Waits

• Segments by Global Cache Buffer Busy

• Segments by CR Blocks Received

• Segments by Current Blocks Received

Advisory Statistics

• Undo Segment Summary

• Undo Segment Stats

Undo Statistics

• Latch Activity

• Latch Sleep Breakdown

• Latch Miss Sources

• Parent Latch Statistics

• Child Latch Statistics

Latch Statistics


• Dictionary Cache Stats

• Dictionary Cache Stats (RAC)

Dictionary Cache Statistics

• Streams CPU/IO Usage

• Streams Capture

• Streams Apply

• Buffered Queues

• Buffered Subscribers

• Rule Set

Streams Statistics

• Library Cache Activity

• Library Cache Activity (RAC)

Library Cache Statistics

• Process Memory Summary

• SGA Memory Summary

• SGA breakdown difference

Memory Statistics Resource Limit Statistics

Init.ora Parameters

Overall CR Flow Diagram

LMS

LMS

FG

LMS

LGWRDatabase

Requestor

Node

Master

Node

Holder

Node

Log

(3) Send

information

to LMS

including

(port,IP)

address

for answer

(6)

(7)

(5)

ask

LGWR

to flush

REDO

(2)

no conflict mode

so grant LOCK

(4 ’)read since

LOCK is

granted

(5 ’)

Context Switch

Interconnect

Message

I/O

(1)

ask for CR

and LOCK

in SHARE

mode

(3 ’) AST

for conversion

(4) Build CR block

and stop when

completed or IO

required(8)

(10) Send CR

buffer

Read With No Transfer

1 2

3 4

Read to Read Transfer

1 2

3 4

Read to Writer Transfer

1 2

3 4

Write to Writer Transfer

1 2

3 4

Write to Read Transfer

1 2

3 4

Writing Dirty Blocks

1 2

3 4

DBA_HIST_SYSSTAT & OSSTAT

User calls

select snap_id,stat_name,

nvl(value,0) - nvl(lag(value) over (partition by stat_name order by snap_id),0) delta

from dba_hist_sysstat

where dbid=1134139816

and instance_number=4

and snap_id between 22199 and 22203

and stat_name='user calls‘ ;

CPU

select snap_id ,

decode ( max(decode(stat_name, 'USER_TIME', delta, 0)) + max(decode(stat_name, 'SYS_TIME', delta, 0))

+ max(decode(stat_name, 'IDLE_TIME', delta, 0)),0,0, max(decode(stat_name, 'USER_TIME', delta, 0)) /

( max(decode(stat_name, 'USER_TIME', delta, 0)) + max(decode(stat_name, 'SYS_TIME', delta, 0)) +

max(decode(stat_name, 'IDLE_TIME', delta, 0)) ))

from

( select snap_id, stat_name,nvl(value,0) - nvl(lag(value) over (partition by stat_name order by snap_id),0) delta ,

value

from dba_hist_osstat

where dbid=1134139816 and instance_number=4 and snap_id between 22199 and 22203

and stat_name in ( 'USER_TIME','SYS_TIME','IOWAIT_TIME','IDLE_TIME')

)

where a.snap_id > 22199 group by snap_id ;

Statistic : V$SYSSTAT General Check Statistics

Statistic Name Statistics Descriptions

consistent gets from cacheNumber of times a consistent read was requested for a block from

buffer cache.

CPU used by this session

Amount of CPU time (in 10s of milliseconds) used by a session from the

time a user call starts until it ends. If a user call completes within 10

milliseconds, the start and end user-call time are the same for purposes

of this statistics, and 0 milliseconds are added.

db block changes

Closely related to "consistent changes", this statistic counts the total

number of changes that were part of an update or delete operation that

were made to all blocks in the SGA. Such changes generate redo log

entries and hence become permanent changes to the database if the

transaction is committed.

This approximates total database work. It statistic indicates the rate at

which buffers are being dirtied (on a per-transaction or per-second basis,

for example).

db block gets from cacheNumber of times a CURRENT block was requested from the buffer

cache. This is a subset of "db block gets" statistics value

execute countTotal number of calls (user and recursive) that executed SQL

statements



logons cumulative

Total number of logons since the instance started. Useful only in

V$SYSSTAT. It gives an instance overview of all processes that logged

on.

parse count ( hard )

Total number of parse calls (real parses). A hard parse is a very

expensive operation in terms of memory use, because it requires Oracle

to allocate a workheap and other memory structures and then build a

parse tree

parse count ( total )

Total number of parse calls (hard and soft). A soft parse is a

check on an object already in the shared pool, to verify that the

permissions on the underlying object have not changed

parse time cpuTotal CPU time used for parsing (hard and soft) in 10s of

milliseconds

parse time elapsed

Total elapsed time for parsing, in 10s of milliseconds. Subtract

"parse time cpu" from the this statistic to determine the total

waiting time for parse resources



physical readsTotal number of data blocks read from disk. This value can be greater

than the value of "physical reads direct" plus "physical reads cache" as

reads into process private buffers also included in this statistic.

physical reads cacheTotal number of data blocks read from disk into the buffer cache. This is

a subset of "physical reads" statistic

physical reads direct

Number of reads directly from disk, bypassing the buffer cache. For

example, in high bandwidth, data-intensive operations such as parallel

query, reads of disk blocks bypass the buffer cache to maximize transfer

rates and to prevent the premature aging of shared data blocks resident

in the buffer cache

physical writesTotal number of data blocks written to disk. This statistics value equals

the sum of "physical writes direct" and "physical writes from cache"

values

physical writes directNumber of writes directly to disk, bypassing the buffer cache (as in a

direct load operation)

redo entriesNumber of times a redo entry is copied into the redo log buffer

redo log space requestsNumber of times the active log file is full and Oracle must wait for disk

space to be allocated for the redo log entries. Such space is created by

performing a log switch



redo size Total amount of redo generated in bytes

session logical reads

The sum of "db block gets" plus "consistent gets". This

includes logical reads of database blocks from either the buffer

cache or process private memory

sorts ( disk ) Number of sort operations that required at least one disk write

sorts ( memory )Number of sort operations that were performed completely in memory

and did not require any disk writes

user callsNumber of user calls such as login, parse, fetch, or execute

user commits

Number of user commits. When a user commits a transaction, the redo

generated that reflects the changes made to database blocks must be

written to disk. Commits often represent the closest thing to a user

transaction rate

user rollbacksNumber of times users manually issue the ROLLBACK statement or an

error occurs during a user's transactions

Statistic : V$SYSSTAT RAC Related Statistics


DBWR fusion writes

1. Fusion writes occur when a block previously changed by another

instance needs to be written to disk in response to a checkpoint or

cache aging

2. Oracle sends a message to notify the other instance that a fusion

write will be performed to move the data block to disk

3. Fusion writes do not require an additional write to disk

4. Fusion writes are a subset of all physical writes incurred by an

instance

gcs messages sentlms및 lck에 의해 수행되는 gcs service에 대한 메시지임.

ges messages sentlmd및 lmon에 의해 수행되는 ges / cgs service에 대한 메시지임.

gc cr blocks receivedTotal number of consistent read blocks successfully received from

another instance.

gc cr block receive timeAccumulated round-trip time for all requests for consistent read blocks.

gc current blocks receivedNumber of current blocks received from the holding instance over the

interconnect

gc current block receive

time Accumulated round trip time for all requests for current blocks



gc cr blocks servedNumber of requests for a CR block served by LMS

gc cr block build timeThe time that the LMS process requires to create a CR block on the

holding instance.

gc cr block flush timeTime waited for a log flush when a CR request is served (part of the

serve time)

gc cr block send timeTime required by LMS to initiate a send of the CR block.

gc current blocks servedThe number of current blocks shipped to the requesting instance over

the interconnect

gc current block pin timeThe time it takes to pin the current block before shipping it to the

requesting instance. Pinning is necessary to disallow changes to the

block while it is prepared to be shipped to another instance

gc current block flush timeThe time it takes to flush the changes to a block to disk (forced log

flush), before the block is shipped to the requesting instance

gc current block send timeThe time it takes to send the current block to the requesting instance

over the interconnect



gc blocks lostBlock losses during transfers. May indicate network problems.

gc blocks corruptBlocks that were corrupted during transfer. High values indicate an IPC,

network, or hardware problem.

Wait Event : V$SESSION_WAIT General Check Wait Event

NAME Description CLASS

enq: TX - row lock

contention

when a session is waiting for a row level lock that is already held

by another session APPLICATION

gc buffer busyThis event indicates that the block was pinned or held up by a

session on a remote instance. CLUSTER

gc cr block 2-way CR block received from master node ( master node=holder node) CLUSTER

gc cr block 3-wayCR block received from holder node ( master node != holder

node) CLUSTER

gc cr block busythe remote instance received the block after a remote instance

processing delay. In most cases, this is due to a log flush. CLUSTER

gc cr block lost The cr block request lost CLUSTER

gc cr block

request Placeholder event which is active while waiting for a block CLUSTER

log file sync

When a user session commits (or rolls back), the session's redo information must be flushed to

the redo logfile by LGWR.

The server process performing the COMMIT or ROLLBACK waits under this event for the write to

the redo log to complete. COMMIT


NAME CLASS

buffer busy waits

This wait indicates that there are some buffers in the buffer

cache that multiple processes are attempting to access

concurrently. Query V$WAITSTAT for the wait statistics for each

class of buffer. Common buffer classes that have buffer busy

waits include data block, segment header, undo header, and

undo block. Concurrency

latch: cache buffers chains

The cache buffers chains latches are used to protect a buffer list

in the buffer cache. These latches are used when searching for,

adding, or removing a buffer from the buffer cache. Contention

on this latch usually means that there is a block that is greatly

contended for (known as a hot block). Concurrency

latch: shared pool Shared pool latch contention Concurrency

row cache lock The session is trying to get a data dictionary lock. Concurrency

library cache pin

This event manages library cache concurrency. Pinning an object

causes the heaps to be loaded into memory. If a client wants to

modify or examine the object, the client must acquire a pin after

the lock. Concurrency


NAME CLASS

library cache lock

This event controls the concurrency between clients of the library

cache. It acquires a lock on the object handle so that either:

•One client can prevent other clients from accessing the same

object

•The client can maintain a dependency for a long time which

does not allow another client to change the object

This lock is also obtained to locate an object in the library cache. Concurrency

enq: HW -contention

The HW enqueue is used to serialize the allocation of space beyond the high water mark of a segment. Configuration

enq: SQ -contention Sequence number enqueue Configuration

enq: TT -contention Temporary table enqueue Configuration

enq: TX - allocate ITL entry

The number of ITL slots in any block in an object is controlled by

the INITRANS and MAXTRANS attributes. INITRANS is the

number of slots initially created in a block when it is first used,

while MAXTRANS places an upper bound on the number of

entries allowed. Each transaction which wants to modify a block

requires a slot in this 'ITL' list in the block. Configuration


NAME CLASS

free buffer waits

This wait event indicates that a server process was unable to find

a free buffer and has posted the database writer to make free

buffers by writing out dirty buffers. A dirty buffer is a buffer whose

contents have been modified. Dirty buffers are freed for reuse

when DBWR has written the blocks to disk. Configuration

latch: redo copy

When a sessions redo buffer is larger than Parameter:

log_small_entry_max_size the kernel first allocates a redo copy

buffer, protected by a redo copy latch.

The buffer will not be used until space is allocated on the log

buffer and some header has been set. However, the redo copy

latch is acquired to reduce the code inside the allocation latch

holding and to prevent further contention. Configuration

log buffer spaceThe system is waiting for space in the log buffer because data is

being written into the log buffer faster than LGWR can write it out. Configuration


NAME CLASS

log file switch (archiving needed)

Waiting for a log switch because the log that the LGWR will be

switching into has not been archived yet. Check the alert file to

make sure that archiving has not stopped due to a failed archive

write. To speed archiving, consider adding more archive

processes or putting the archive files on striped disks. Configuration

log file switch (checkpoint incomplete)

Waiting for a log switch because the session cannot wrap into the

next log. Wrapping cannot be performed because the checkpoint

for that log has not completed Configuration

log file switch completion Waiting for a log switch to complete. Configuration

enq: US -contention Undo segment DDL Other

latch freeThe process waits for a latch that is currently busy (held by

another process). Other

DFS lock handle

The session waits for the lock handle of a global lock request. The lock handle identifies a global lock. With this lock handle, other operations can be performed on this global lock (to identify the global lock in future operations such as conversions or release). The global lock is maintained by the DLM. Other


NAME CLASS

db file parallel write

This event occurs in the DBWR. It indicates that the DBWR is performing a parallel write to files and blocks. When the last I/O has gone to disk, the wait ends. System I/O

log file parallel write

This event involves writing redo records to the redo log files from

the log buffer. System I/O

log file sequential read

Waiting for the read from this logfile to return. This is used to read

redo records from the log file. System I/O

log file single write

Waiting for the write to this logfile to complete. This event is used

while updating the header of the logfile. It is signaled when

adding a log file member and when incrementing sequence

numbers. System I/O

db file parallel read

This happens during recovery. It can also happen during buffer

prefetching, as an optimization (rather than performing multiple

single-block reads). Database blocks that need to be changed as

part of recovery are read in parallel from the database. User I/O

db file sequential read

This event signifies that the user process is reading a buffer into

the SGA buffer cache and is waiting for a physical I/O call to

return. A sequential read is a single-block read. User I/O

db file single write This event is used to wait for the writing of the file headers. User I/O


NAME CLASS

db file scattered read

A db file scattered read issues a scattered read to read the data

into multiple discontinuous memory locations. A scattered read is

usually a multiblock read. It can occur for a fast full scan (of an

index) in addition to a full table scan. User I/O

direct path write / temp

During Direct Path operations, the data is asynchronously written

to the database files. At some stage the session needs to make

sure that all outstanding asynchronous I/O have been completed

to disk. This can also happen if, during a direct write, no more

slots are available to store outstanding load requests User I/O

direct path read / temp

During Direct Path operations the data is asynchronously read

from the database files. At some stage the session needs to

make sure that all outstanding asynchronous I/O have been

completed to disk. This can also happen if during a direct read no

more slots are available to store outstanding load requests User I/O

Documents

- DBGuide.net · 2010-03-30 · Viewing AWR Report AWR Report displays all statistics captured over a snapshot range Roughly equivalent to the STATSPACK