ORA-12547: TNS:lost contact

Issue:

We are doing database upgrade and suddenly when we try to connect to database as sysdba, started seeing ora-12547 error as below:

[oracle@oradb1 19.3.0]$ sqlplus / as sysdba

 

SQL*Plus: Release 19.0.0.0.0 - Production on Fri Jan 7 09:59:41 2022

Version 19.13.0.0.0

 

Copyright (c) 1982, 2021, Oracle. All rights reserved.

ERROR:

ORA-12547: TNS:lost contact

We verified database processes and running fine but still unable to connect to database. Tried connecting as sys or system user and still having same issue.

We are able to connect to database via listener successfully.

Cause:

spfile has been corrupted as it has been accidentally edited by some one. Got below error when tried creating pfile from spfile.

SQL> create pfile from spfile;

create pfile from spfile*

ERROR at line 1:

ORA-01565: error in identifying file '?=/dbs/spfile@.ora'

ORA-27046: file size is not a multiple of logical block size

Additional information: 1

Fix:

Upon further investigation, We identified that spfile has been accidentally edited by someone making the file corrupt.

Performed action plan as below:

1) Connect to database as sys user with TNS

2) shut down  database (if required,  get parameter detaisl from database before shutdown)

3) create pfile/spfile manually from backup

4) Startup database