Oracle RAC 19C PDB instance is down

Linux oracle 19c rac Environmental Science ,7 month 20 Early morning 0 About five o'clock pdb Database down , Check the alarm log and find

rrors in file /oracle/app/oracle/diag/rdbms/rmscdb/rmscdb2/trace/rmscdb2_o000_43454.trc (incident=128972) (PDBNAME=CDB$ROOT):
ORA-00603: ORACLE server session terminated by fatal error
ORA-27504: IPC error creating OSD context
ORA-27300: OS system dependent operation:sendmsg failed with status: 105
ORA-27301: OS failure message: No buffer space available
ORA-27302: failure occurred at: sskgxpsnd2
2022-07-20T00:05:01.929059+08:00
Errors in file /oracle/app/oracle/diag/rdbms/rmscdb/rmscdb2/trace/rmscdb2_rms0_160427.trc (incident=102889) (PDBNAME=CDB$ROOT):
ORA-00240: control file enqueue held for more than 120 seconds

May be ORA-00240 Caused by the , But the query document may be bug, But this bug stay oracle18c Fixed , At present, I don't know what's going on ？

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Other answers 1：

Upload attachments ： alert_rmscdb1.log

Other answers 2：

ORA-27301: OS Failure Message: No Buffer Space Available / ORA-27302: failure occurred at: sskgxpsnd2 Source Script ( file ID 2322410.1)

Other answers 3：

1、 stay /etc/sysctl.conf add vm.min_free_kbytes Parameters ,vm.min_free_kbytes= Memory *0.4%( For example, memory. 8g, that vm.min_free_kbytes=8*1024*1024*0.004）

2、 modify lo mtu by 16436.

Temporary modification ifconfig lo mtu 16436

Or permanently modified vi /etc/sysconfig/network-scripts/ifcfg-lo MTU=16436

Look at this. , The problems encountered are the same as yours

https://cloud.tencent.com/developer/article/1863289

Other answers 4：

Send this trace Well ：

/oracle/app/oracle/diag/rdbms/rmscdb/rmscdb2/trace/rmscdb2_rms0_160427.trc