内存故障案例-文件句柄溢出（MOS文档）

张伟倩

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2020-03-18

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2020/3/18 Document 1321306.1

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In this Document

Goal

Solution

References

APPLIES TO:

Oracle Database - Enterprise Edition - Version 11.1.0.7 and later

Oracle Database Cloud Schema Service - Version N/A and later

Oracle Database Exadata Cloud Machine - Version N/A and later

Oracle Cloud Infrastructure - Database Service - Version N/A and later

Oracle Database Cloud Exadata Service - Version N/A and later

Linux x86

Linux x86-64

***Checked for relevance on 22-May-2013***

GOAL

Oracle is creating hundreds of thousands open file descriptors in /dev/shm (open files)

$ lsof -n | grep /dev/shm | wc -l

247455

But there are only just hundreds of files in /dev/shm

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Document Details

Type:

Status:

Last Major

Update:

Last Update:

HOWTO

PUBLISHED

04-Aug-2018

19-Nov-2019

Related Products

Oracle Database - Enterprise

Edition

Oracle Database Cloud Schema

Service

Gen 1 Exadata Cloud at

Customer (Oracle Exadata

Database Cloud Machine)

Oracle Cloud Infrastructure -

Database Service

Oracle Database Cloud Exadata

Service

Information Centers

Information Center: Overview

Database Server/Client

Why Does Oracle Create So Many Open File Descriptors in /dev/shm on Linux When memory_target is Set ? (Doc ID

1321306.1)

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2020/3/18 Document 1321306.1

https://support.oracle.com/epmos/faces/DocumentDisplay?_afrLoop=293783104328168&id=1321306.1&_afrWindowMode=0&_adf.ctrl-state=s1e4cf916_178 2/5

$ ls -l /dev/shm/* | wc -l

262

1. Why is Oracle keeping hundreds of thousands Open File descriptors in /dev/shm while there are just hundreds of files ?

2. Is this a known issue? ( any notes/documents/bug reports/fixes exist).

3. Or is this expected behavior of oracle?

SOLUTION

1) Let's use a test database (11.1.0.7) to demonstrate how Automatic Memory Management uses file descriptors and why there are so many

Open File descriptors.

A) Before starting the 11.1.0.7 database, /dev/shm is empty and there are no open files

$ ls -l /dev/shm

total 0

$ lsof -n | grep /dev/shm

B) Let's start the database, then check /dev/shm

UNIX> sqlplus " / as sysdba"

SQL*Plus: Release 11.1.0.7.0 - Production on Fri May 6 14:57:28 2011

Connected to an idle instance.

SQL> startup

ORACLE instance started.

Total System Global Area 845348864 bytes

Fixed Size 1316656 bytes

Variable Size 578816208 bytes

Database Buffers 260046848 bytes

Redo Buffers 5169152 bytes

Database mounted.

Database opened.

SQL> show parameter memory_target

Installation and

Upgrade/Migration [1351022.2]

Index of Oracle Database

Information Centers

[1568043.2]

インフォメーション・センタ

ー: データベースおよび

Enterprise Manager 日本語ドキ

ュメント [1946305.2]

Information Center: Overview

of Database Security Products

[1548952.2]

Platform as a Service (PaaS)

and Oracle Cloud Infrastructure

(OCI) Information Center

[2048297.2]

Document References

Open Files/Open File

Descriptors [787780.1]

How To Determine Granule

Size [947152.1]

Recently Viewed

HugePages on Oracle Linux

64-bit [361468.1]

ALERT: Disable Transparent

HugePages on SLES11,

RHEL6, RHEL7, OL6, OL7,

and UEK2 and above

[1557478.1]

WAITEVENT: "log file sync"

Reference Note [34592.1]

SRDC - 如何收集 ‘log file

sync’ 等待是数据库主要等待

事件问题的标准信息

[2367701.1]

SRDC - 对于 SQL 性能问题如

何收集诊断信息 [2293025.1]

2020/3/18 Document 1321306.1

https://support.oracle.com/epmos/faces/DocumentDisplay?_afrLoop=293783104328168&id=1321306.1&_afrWindowMode=0&_adf.ctrl-state=s1e4cf916_178 2/5

$ ls -l /dev/shm/* | wc -l

262

1. Why is Oracle keeping hundreds of thousands Open File descriptors in /dev/shm while there are just hundreds of files ?

2. Is this a known issue? ( any notes/documents/bug reports/fixes exist).

3. Or is this expected behavior of oracle?

SOLUTION

1) Let's use a test database (11.1.0.7) to demonstrate how Automatic Memory Management uses file descriptors and why there are so many

Open File descriptors.

A) Before starting the 11.1.0.7 database, /dev/shm is empty and there are no open files

$ ls -l /dev/shm

total 0

$ lsof -n | grep /dev/shm

B) Let's start the database, then check /dev/shm

UNIX> sqlplus " / as sysdba"

SQL*Plus: Release 11.1.0.7.0 - Production on Fri May 6 14:57:28 2011

Connected to an idle instance.

SQL> startup

ORACLE instance started.

Total System Global Area 845348864 bytes

Fixed Size 1316656 bytes

Variable Size 578816208 bytes

Database Buffers 260046848 bytes

Redo Buffers 5169152 bytes

Database mounted.

Database opened.

SQL> show parameter memory_target

Installation and

Upgrade/Migration [1351022.2]

Index of Oracle Database

Information Centers

[1568043.2]

インフォメーション・センタ

ー: データベースおよび

Enterprise Manager 日本語ドキ

ュメント [1946305.2]

Information Center: Overview

of Database Security Products

[1548952.2]

Platform as a Service (PaaS)

and Oracle Cloud Infrastructure

(OCI) Information Center

[2048297.2]

Document References

Open Files/Open File

Descriptors [787780.1]

How To Determine Granule

Size [947152.1]

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