This document provides recommendations for system capacity planning for an Oracle database: - Plan for 1 CPU per 200 concurrent users and prefer medium speed CPUs over fewer faster CPUs. - Reserve 10% of memory for the operating system and allocate 220 MB for the Oracle SGA and 3 MB per user process. - Use striped and mirrored or striped with parity RAID for disks. Consider raw devices or SANs if possible. - Ensure the network capacity is adequate based on site size.

1. System Capa Planning
2004 . 07
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연성석

2. System Capa Planing
• Typically 1 CPU per 200 concurrent users
• More medium speed CPUs are usually better
than fewer faster CPUs
• 10% of memory for operating system, 220 MB
for Oracle SGA and 3 MB per user process
• Disks should ideally be striped and mirrored
RAID0/RAID1 or striped with parity RAID5

3. System Capa Planning(cont.)
• Consider raw devices to take pressure
off your CPUs
• Consider SANs if budget permits –
SANs make heavy usage of disk cache
• Make sure that your network is
adequate – 256k for smaller site and
2Mbit+ for larger sites

4. System Capa Planning(cont.)
• 1GB RAM - OLTP by Oracle docs
- 200MB for operation system
- 0.8 * (1GB - 200MB) = 640MB for SGA
- 0.2 * (1GB - 200MB) = 160MB for PGA

5. System Capa Planning(cont.)
• Logical reads > 10,000(100MHz CPU)/sec
- usualy 100MHZ , 1 cpu당
- if 1GHZ 이면 100,000 blocks/sec 가능
• Physical reads > 100 disk/sec
• Hard, Soft Parses > 100, 300/sec
• SUN 의 filesystem 이 UFS이면 disk I/O 가 별로 안좋
다. 또한 async I/O 를 쓰면 더욱 안 좋음.
- 이때는 raw device 또는 QUICK I/O를 쓰면됨
(veritas 제품중 quick I/O 를 지원하는것도 있음)
성능 향상율은 약 30 ~ 50% 정도

6. System Capa Planning(cont.)
• Maximum Tolerated Oracle Kernal Event Latencies
Event
Max. tolerated latency
per event
Events-persecond
rate at
this latency
Single-block disk read (PIO) 10 ms 0.01 s 100
Single-block access from Oracle
buffer cache (LIO), 500 MHz CPU
20 μs 0.000 02 s 50,000
Single-block access from Oracle
buffer cache (LIO), 1 GHz CPU
10 μs 0.000 01 s 102,400
Single-block access from Oracle
buffer cache (LIO), 2 GHz CPU
5 μs 0.000 005 s 204,800
SQL*Net transmission via WAN 200 ms 0.2 s 5
SQL*Net transmission via LAN 15 ms 0.015 s 67
SQL*Net transmission via IPC 1 ms 0.001 s 1,000

7. Appendix - 시간 단위 환산
1일 day 86,400 s 24 h
1시간 h 3,600 s 60 min
1분 min 60 s
1초 s (sec)
1센티초 cs(csec) 10-2
1밀리초 ms (msec) 10-3 s 1 s / 1 000 = 0.001
1마이크로초 μs (μsec) 10-6 s 1 s / 1 000 000 = 0.000 001
1나노초 ns (nsec) 10-9 s 1 s / 1 000 000 000 = 0.000 000 001
1피코초 ps 10-12 s 1 s / 1 000 000 000 000 = 0.000 000 000 001
1펨토초 fs 10-15 s 1 s / 1 000 000 000 000 000 = 0.000 000 000 000 001
1아토초 as 10-18 s 1 s / 1 000 000 000 000 000 000 = 0.000 000 000 000 000 001

8. 주요 Wait Event별 Root Cause
• db file sequintial/scattered reads
-> SQL by buffer gets/disk reads, file I/O stats
• CPU Time
-> Parse rates, Sorts, SQL executions, SQL by buffer gets/disk reads,
SMP processes(bugs)
• direct path read/write
-> sort/hash joins, parallel, sort/hash_area_size, file I/O stats
• buffer busy waits
-> buffer pool, buffer waits, file I/O stats, segment statistics