今天上午接到电话，用户反映一套10.2.0.4的数据库出现用户无法登录的症状，随即在家里连上VPN远程支持，登上主机以后尝试测试操作系统认证登录和远程登录，发现已经能够正常登录了；为了了解起因，去查看了告警日志alert.log，发现在11:00左右出现大量的ksvcreate:process creation failed错误，具体错误日志如下:
Wed Mar 23 10:00:17 2011
Process m000 died, see its trace file
Wed Mar 23 10:00:17 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 10:01:18 2011
Process m000 died, see its trace file
Wed Mar 23 10:01:18 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 10:02:19 2011
Process m000 died, see its trace file
Wed Mar 23 10:02:19 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 10:54:41 2011
Process P007 died, see its trace file
Wed Mar 23 10:56:40 2011
Process P007 died, see its trace file
Wed Mar 23 10:57:40 2011
Process P007 died, see its trace file
Wed Mar 23 10:58:40 2011
Process P007 died, see its trace file
Wed Mar 23 10:59:18 2011
Process J000 died, see its trace file
Wed Mar 23 10:59:18 2011
kkjcre1p: unable to spawn jobq slave process
Wed Mar 23 10:59:18 2011
Errors in file /oracle/app/oracle/admin/sdh/bdump/sdh_cjq0_717010.trc:
Wed Mar 23 11:01:00 2011
Process m000 died, see its trace file
Wed Mar 23 11:01:00 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 11:02:01 2011
Process m000 died, see its trace file
Wed Mar 23 11:02:01 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 11:02:40 2011
Process P007 died, see its trace file
Wed Mar 23 11:03:02 2011
Process m000 died, see its trace file
Wed Mar 23 11:03:02 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 11:04:03 2011
Process m000 died, see its trace file
Wed Mar 23 11:04:03 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 11:04:40 2011
Process P007 died, see its trace file
ksvcreate: Process creation failed错误信息一般在Oracle实例在创建一些辅助后台进程(如mmon的子进程m00x或者并行子进程p00x等)时出现进程启动失败时出现，而造成该错误的可能性有多种，包括Oracle实例资源不足、操作系统资源不足等等。其中较为常见的是实例instance的process使用达到上限，可以通过查询v$resource_limit视图来了解实例生命周期内是否发生过process总数暴满的情况:
SQL> select * from v$resource_limit;
RESOURCE_NAME CURRENT_UTILIZATION MAX_UTILIZATION INITIAL_ALLOCATION LIMIT_VALUE
------------------------------ ------------------- --------------- -------------------- --------------------
processes 79 800 800 800
sessions 80 813 885 885
enqueue_locks 18 303 10910 10910
enqueue_resources 18 166 4112 UNLIMITED
ges_procs 0 0 0 0
ges_ress 0 0 0 UNLIMITED
ges_locks 0 0 0 UNLIMITED
ges_cache_ress 0 0 0 UNLIMITED
ges_reg_msgs 0 0 0 UNLIMITED
ges_big_msgs 0 0 0 UNLIMITED
ges_rsv_msgs 0 0 0 0
gcs_resources 0 0 0 0
gcs_shadows 0 0 0 0
dml_locks 0 153 3892 UNLIMITED
temporary_table_locks 0 3 UNLIMITED UNLIMITED
transactions 3125 3156 973 UNLIMITED
branches 0 3 973 UNLIMITED
cmtcallbk 0 2 973 UNLIMITED
sort_segment_locks 0 8 UNLIMITED UNLIMITED
max_rollback_segments 19 43 973 65535
max_shared_servers 0 0 UNLIMITED UNLIMITED
parallel_max_servers 6 122 120 3600
/* 可以看到processes的MAX_UTILIZATION最大使用数目曾到过LIMIT_VALUE限定的800，
sessions也有类似的情况 */
从以上V$resource_limit视图的输出来看，极有可能是processes总数达到上限导致了新的后台辅助进程创建失败，其实我们可以很方便地验证这一点:
SQL> select * from v$version;
BANNER
----------------------------------------------------------------
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod
PL/SQL Release 10.2.0.1.0 - Production
CORE 10.2.0.1.0 Production
TNS for Linux: Version 10.2.0.1.0 - Production
NLSRTL Version 10.2.0.1.0 - Production
SQL> alter system set processes=20 scope=spfile;
System altered.
/* 将processes参数修改到一个较小值 */
SQL> startup force;
ORACLE instance started.
SQL> select resource_name,MAX_UTILIZATION,LIMIT_VALUE from v$resource_limit where resource_name in ('processes','sessions');
RESOURCE_NAME MAX_UTILIZATION LIMIT_VALUE
------------------------------ --------------- ---------------
processes 20 20
sessions 19 27
/* 从以上输出可以看到process总数曾经到达20的上限 */
/* 观察告警日志可以看到相关ksvcreate: Process(m000) creation failed的记录 */
[maclean@rh8 bdump]$ tail -20 alert_PROD1.log
ksvcreate: Process(m000) creation failed
Process m000 died, see its trace file
Wed Mar 23 22:01:52 2011
ksvcreate: Process(m000) creation failed
Wed Mar 23 22:01:55 2011
Process q000 died, see its trace file
Wed Mar 23 22:01:55 2011
ksvcreate: Process(q000) creation failed
Wed Mar 23 22:02:07 2011
Process q000 died, see its trace file
Wed Mar 23 22:02:07 2011
ksvcreate: Process(q000) creation failed
Wed Mar 23 22:02:19 2011
Process q000 died, see its trace file
Wed Mar 23 22:02:19 2011
ksvcreate: Process(q000) creation failed
Wed Mar 23 22:02:31 2011
Process q000 died, see its trace file
Wed Mar 23 22:02:31 2011
ksvcreate: Process(q000) creation failed
不同于10g，在11g中类似的错误出现后会在告警日志中说明process creation即进程创建失败的具体原因，如进程总数达到上限，那么就会出现ORA-00020错误(maximum number of processes (%s) exceeded. All process state objects are in use.Increase the value of the PROCESSES initialization parameter),类似以下日志:
ORA-00020: No more process state objects available
ORA-20 errors will not be written to the alert log for
the next minute. Please look at trace files to see all
the ORA-20 errors.
Process m001 submission failed with error = 20
Process m002 submission failed with error = 20
Process m003 submission failed with error = 20
Process m003 submission failed with error = 20
Process m002 submission failed with error = 20
2011-03-23 22:10:07.037000 +08:00
Process q001 submission failed with error = 20
实际上ksvcreate: Process creation failed错误在能够了解其发生的root cause的情况下，并不难解决。在上例中我们可以清楚地了解到是因为数据库在实际运行中出现了processes进程总数达到参数设定上限从而导致问题出现，那么可以合理增加初始化参数processes或者通过修正异常频繁的程序客户端登录来解决该问题。