启动数据库报错ORA-09968，且出现pga_aggregate_limit value is too high的告警

系统：centos 7.9 64位
数据库：oracle 12.2.0.1 64位
环境：单实例 + noncdb + 物理内存 4g
问题描述：启动数据库报错ORA-09968，且出现pga_aggregate_limit value is too high的告警，如下所示：
1、异常告警
启动到mount出现ORA-01102。
idle 15-OCT-22> startup mount
ORACLE instance started.

Total System Global Area 2533359616 bytes
Fixed Size                  8623880 bytes
Variable Size             687868152 bytes
Database Buffers         1828716544 bytes
Redo Buffers                8151040 bytes
ORA-01102: cannot mount database in EXCLUSIVE mode

trace文件显示如下.
Starting background process LGWR
2022-10-15T00:06:02.787145+08:00
WARNING: pga_aggregate_limit value is too high for the
amount of physical memory on the system
  PGA_AGGREGATE_LIMIT is 2048 MB
  PGA_AGGREGATE_TARGET is 604 MB.
  physical memory size is 3770 MB
  limit based on physical memory and SGA usage is 977 MB
  SGA_TARGET is 2416 MB
2022-10-15T00:06:06.111674+08:00
Using default pga_aggregate_limit of 2048 MB
2022-10-15T00:06:07.304102+08:00
LGWR started with pid=20, OS id=9621 
2022-10-15T00:06:07.315238+08:00
Starting background process CKPT
2022-10-15T00:06:07.472158+08:00
CKPT started with pid=8, OS id=9640 
Starting background process SMON
2022-10-15T00:06:07.525671+08:00
LGWR slave LG00 created with pid=21, OS pid=9644
2022-10-15T00:06:07.572361+08:00
SMON started with pid=22, OS id=9646 
LGWR slave LG01 created with pid=23, OS pid=9650
Starting background process SMCO
Starting background process RECO
2022-10-15T00:06:07.620640+08:00
SMCO started with pid=24, OS id=9653 
2022-10-15T00:06:07.646708+08:00
RECO started with pid=25, OS id=9655 
Starting background process LREG
2022-10-15T00:06:07.676753+08:00
LREG started with pid=27, OS id=9659 
Starting background process PXMN
2022-10-15T00:06:07.724452+08:00
PXMN started with pid=29, OS id=9663 
Starting background process FENC
2022-10-15T00:06:07.743038+08:00
FENC started with pid=30, OS id=9665 
Starting background process MMON
2022-10-15T00:06:07.773322+08:00
MMON started with pid=31, OS id=9667 
Starting background process MMNL
2022-10-15T00:06:07.792956+08:00
MMNL started with pid=32, OS id=9669 
2022-10-15T00:06:07.813840+08:00
starting up 1 dispatcher(s) for network address '(ADDRESS=(PARTIAL=YES)(PROTOCOL=TCP))'...
starting up 1 shared server(s) ...
Starting background process TMON
2022-10-15T00:06:07.896610+08:00
TMON started with pid=34, OS id=9675 
ORACLE_BASE from environment = /u01//app/oracle
2022-10-15T00:06:08.422278+08:00
ALTER DATABASE   MOUNT
2022-10-15T00:06:08.433345+08:00
sculkget: failed to lock /u01//app/oracle/product/12.2.0/db/dbs/lkORCL exclusive
sculkget: lock held by PID: 8221
2022-10-15T00:06:08.439347+08:00
ORA-09968: unable to lock file
Linux-x86_64 Error: 11: Resource temporarily unavailable
Additional information: 8221
ORA-1102 signalled during: ALTER DATABASE   MOUNT...
2022-10-15T01:05:05.258705+08:00
Resize operation completed for file# 3, old size 471040K, new size 481280K


ALTER DATABASE   MOUNT
2022-10-15T10:05:51.341444+08:00
sculkget: failed to lock /u01//app/oracle/product/12.2.0/db/dbs/lkORCL exclusive
sculkget: lock held by PID: 1956
2022-10-15T10:05:51.341763+08:00
ORA-09968: unable to lock file
Linux-x86_64 Error: 11: Resource temporarily unavailable
Additional information: 1956
ORA-1102 signalled during: ALTER DATABASE   MOUNT...
2022-10-15T10:05:52.042139+08:00
Using default pga_aggregate_limit of 2048 MB

2、异常原因
a、对于pga_aggregate_limit告警，原因为物理内存设置过小；
b、对于ORA-09968告警，是由于在startup nomount过程中shm共享内存和共享的信号均未建立，若同时startup可能会启动2套实例.此时便使用lk$oracle_sid文件，先锁住该文件的实例就优先继续后面的启动过程.
3、处理过程
a、调整虚拟机内存为8g.
b、删除lk$ORACLE_SID文件
# cd /u01/app/oracle/product/12.2.0/db/dbs
# rm -rf lkORCL
c、调整内存
将数据库启动到mount阶段,调整数据库内存.
idle 15-OCT-22> alter system set sga_target=3500m scope=spfile;

System altered.

idle 15-OCT-22> alter system set sga_max_size=3500m scope=spfile;

System altered.

idle 15-OCT-22> alter system set pga_aggregate_target=2300m scope=spfile;

System altered.

此后重启数据库，无异常发生.

参考网址：https://blog.csdn.net/oradbm/article/details/103900160