杨廷琨（yangtingkun）
云和恩墨 CTO
高级咨询顾问，Oracle ACE 总监，ITPUB Oracle 数据库管理版版主
编辑手记：在很多数据库的故障案例中，一个简单的疏忽可能导致问题被层层放大，最终导致故障，这就是蝴蝶效应的传播原理。这里分享的小案例自顶向下的追溯可以显见：实例挂起->归档失败->实例错误->参数配置。根本的原因往往很简单，DBA的严谨尤其重要。
客户的11.2.0.3 RAC数据库出现了归档失败的情况，导致单个实例出现HANG死的状况。
检查错误信息发现：
Tue Jul 02 16:49:13 2013
ARC1: Error 19504 Creating archive log file TO '+DATA02'
ARCH: Archival stopped, error occurred. Will continue retrying
ORACLE Instance orcl1 - Archival Error
ORA-16038: log 14 SEQUENCE# 68244 cannot be archived
ORA-19504: failed TO CREATE file ""
ORA-00312: online log 14 thread 1: '+DATA02/orcl/onlinelog/group_14.264.792274883'
ORA-00312: online log 14 thread 1: '+DATA02/orcl/onlinelog/group_14.265.792274889'
Archiver process freed FROM errors. No longer stopped
Tue Jul 02 16:50:37 2013
ARC0: LGWR IS actively archiving destination LOG_ARCHIVE_DEST_3
ARCH: Archival stopped, error occurred. Will continue retrying
ORACLE Instance orcl1 - Archival Error
ORA-16014: log 14 SEQUENCE# 68244 NOT archived, no available destinations
ORA-00312: online log 14 thread 1: '+DATA02/orcl/onlinelog/group_14.264.792274883'
ORA-00312: online log 14 thread 1: '+DATA02/orcl/onlinelog/group_14.265.792274889'
ARC0: Archive log rejected (thread 1 SEQUENCE 68240) at host 'orclsh'
FAL[server, ARC0]: FAL archive failed, see trace file.
ARCH: FAL archive failed. Archiver continuing
ORACLE Instance orcl1 - Archival Error. Archiver continuing.
由于归档失败发生在ASM磁盘上，首先检查ASM磁盘空间以及DB_RECOVERY_FILE_DEST_SIZE，ASM磁盘空间是足够的，而且由于只有一个节点出现出现了无法归档的问题，也可以排除是空间不足造成的。
确认两个节点的DB_RECOVERY_FILE_DEST_SIZE参数设置都是0，基本上可以判断问题和当前节点的ASM实例状态不正常有关。
接下来检查ASM实例的错误信息：
Tue Jul 02 16:41:43 2013
Dumping diagnostic DATA IN directory=[cdmp_20130702164115], requested BY (instance=2, osid=2032294 (LMD0)), summary=[incident=165521].
Tue Jul 02 16:49:13 2013
Dumping diagnostic DATA IN directory=[cdmp_20130702164845], requested BY (instance=2, osid=2032294 (LMD0)), summary=[incident=165522].
当前节点ASM实例出现了的这个信息，说明报错发生在实例2上，检查实例2的ASM告警日志文件：
Tue Jul 02 18:29:55 2013
Errors IN file /u01/app/grid/diag/asm/+asm/+ASM2/trace/+ASM2_lmd0_2032294.trc (incident=186256):
ORA-04031: unable TO allocate 3768 bytes OF shared memory ("shared pool","unknown object","sga heap(1,0)","ges enqueues")
USE ADRCI OR Support Workbench TO package the incident.
See Note 411.1 at My Oracle Support FOR error AND packaging details.
Insufficient shared pool TO allocate a GES object (ospid 2032294)
Tue Jul 02 18:29:55 2013
Sweep [inc][186256]: completed
Tue Jul 02 18:36:49 2013
Errors IN file /u01/app/grid/diag/asm/+asm/+ASM2/trace/+ASM2_lmd0_2032294.trc (incident=186257):
ORA-04031: unable TO allocate 3768 bytes OF shared memory ("shared pool","unknown object","sga heap(1,0)","ges enqueues")
USE ADRCI OR Support Workbench TO package the incident.
See Note 411.1 at My Oracle Support FOR error AND packaging details.
Insufficient shared pool TO allocate a GES object (ospid 2032294)
果然实例2上的ASM出现了大量ORA-4031错误，这说明ASM实例的Shared Pool内存可能配置不足。检查ASM启动的参数配置：
Sat Aug 25 20:06:55 2012
NOTE: No asm libraries found IN the system
ERROR: -5(Duplicate disk DATA_DG01:ASM_DISK1)
ERROR: -5(Duplicate disk DATA_DG01:ASM_DISK2)
MEMORY_TARGET defaulting TO 411041792.
* instance_number obtained FROM CSS = 2, checking FOR the existence OF node 0...
* node 0 does NOT exist. instance_number = 2
Starting ORACLE instance (normal)
LICENSE_MAX_SESSION = 0
LICENSE_SESSIONS_WARNING = 0
Private Interface 'en1' configured FROM GPnP FOR USE AS a private interconnect.
[name='en1', TYPE=1, ip=169.254.78.6, mac=00-1a-64-bb-50-7d, net=169.254.0.0/16, mask=255.255.0.0, USE=haip:cluster_interconnect/62]
Public Interface 'en0' configured FROM GPnP FOR USE AS a public interface.
[name='en0', TYPE=1, ip=10.1.16.35, mac=00-1a-64-bb-50-7c, net=10.1.16.32/27, mask=255.255.255.224, USE=public/1]
Picked latch-free SCN scheme 3
USING LOG_ARCHIVE_DEST_1 parameter DEFAULT VALUE AS /u01/app/11.2.0.3/grid/dbs/arch
Autotune OF undo retention IS turned ON.
LICENSE_MAX_USERS = 0
SYS auditing IS disabled
NOTE: Volume support enabled
Starting up:
Oracle DATABASE 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
WITH the REAL Application Clusters AND Automatic Storage Management options.
ORACLE_HOME = /u01/app/11.2.0.3/grid
System name: AIX
Node name: orcldb2
Release: 1
Version: 6
Machine: 00C94E064C00
USING parameter settings IN server-side pfile /u01/app/11.2.0.3/grid/dbs/init+ASM2.ora
System parameters WITH non-DEFAULT VALUES:
large_pool_size = 12M
instance_type = "asm"
remote_login_passwordfile= "EXCLUSIVE"
asm_diskstring = "/dev/ocr_*"
asm_diskstring = "/dev/voting_*"
asm_diskstring = "/dev/asm_*"
asm_diskgroups = "DATA"
asm_diskgroups = "DATA_DG01"
asm_diskgroups = "SPFILE_DG"
asm_power_limit = 1
diagnostic_dest = "/u01/app/grid"
Cluster communication IS configured TO USE the following interface(s) FOR this instance
169.254.78.6
cluster interconnect IPC version:Oracle UDP/IP (generic)
IPC Vendor 1 proto 2
当前ASM实例使用默认的MEMORY_TARGET配置，分配大小大约是400M，根据Oracle的MOS文章：ASM & Shared Pool (ORA-4031) [ID 437924.1]，在11.2.0.3中，Oracle增加了ASM实例所允许的默认进程数PROCESSES，但是默认的MEMORY_TARGET参数没有增加。
根据Oracle的建议，11.2.0.3的MEMORY_TARGET至少应该设置到1536M，而MEMORY_MAX_TARGET设置为4096M。
SQL> ALTER system SET memory_max_target=4096m scope=spfile;
SQL> ALTER system SET memory_target=1536m scope=spfile;
对于当前的情况，如果短时间内无法重启DB和ASM实例，可以在问题节点配置一个第二本地归档路径，设置目标路径为本地磁盘，从而避免归档无法完成而导致的实例HANG死。
本文出自数据和云公众号，原文链接
