BUG #15979: PG_VERSION , pg_tblspc got deleted automatically & postgres server creased.

The following bug has been logged on the website:

Bug reference:      15979
Logged by:          mahesh Shetty
Email address:      maheshetty20@gmail.com
PostgreSQL version: 9.4.4
Operating system:   Oracle Linux Server release 6.7
Description:

Investigation through postmaster while starting the database service to get
DB connect: 
 
-bash-4.1$  /usr/pgsql-9.4/bin/postgres -D /var/lib/pgsql/9.4/data <
2019-08-20 00:13:29.353 CDT >FATAL:  "/var/lib/pgsql/9.4/data" is not a
valid data directory < 2019-08-20 00:13:29.353 CDT >DETAIL:  File
"/var/lib/pgsql/9.4/data/PG_VERSION" is missing.     
There was missing PG_VERSION  which was created manually  
 
-bash-4.1$ postmaster -D /var/lib/pgsql/9.4/data/ < 2019-08-20 00:27:35.275
CDT >FATAL:  could not open directory "pg_tblspc": No such file or directory
-bash-4.1$   
There was missing pg_tblspc  which was created manually 
 
-bash-4.1$  /usr/pgsql-9.4/bin/pg_ctl  -D /var/lib/pgsql/9.4/data/ start  
server starting  
-bash-4.1$ < 2019-08-20 00:29:31.982 CDT >LOG:  redirecting log output to
logging collector process < 2019-08-20 00:29:31.982 CDT >HINT:  Future log
output will appear in directory "pg_log". 
-bash-4.1$ psql -p 1433  
psql: FATAL:  the database system is starting up  
-bash-4.1$ postmaster -D /var/lib/pgsql/9.4/data/ < 2019-08-20 00:29:47.588
CDT >FATAL:  lock file "postmaster.pid" already exists < 2019-08-20
00:29:47.588 CDT >HINT:  Is another postmaster (PID 30083) running in data
directory "/var/lib/pgsql/9.4/data"? -bash-4.1$ psql -p 1433 psql: FATAL:
the database system is starting up 
  
Deleted manually pid files and started postgres service 
-bash-4.1$ /usr/pgsql-9.4/bin/pg_ctl  -D /var/lib/pgsql/9.4/data/ start
pg_ctl: another server might be running; trying to start server anyway
server starting -bash-4.1$ < 2019-08-20 00:31:04.932 CDT >FATAL:  lock file
"postmaster.pid" already exists < 2019-08-20 00:31:04.932 CDT >HINT:  Is
another postmaster (PID 30083) running in data directory
"/var/lib/pgsql/9.4/data"? 
-bash-4.1$ psql -p 1433 psql: FATAL:  the database system is starting up
-bash-4.1$    
 
 
 
Server went into recovery mode as it was stopped abruptly. 
•    postgres 30083     1  0 00:29 pts/1    00:00:00
/usr/pgsql-9.4/bin/postgres -D /var/lib/pgsql/9.4/data 
postgres 30084 30083  0 00:29 ?        00:00:00 postgres: logger process 
postgres 30085 30083 86 00:29 ?        00:01:48 postgres: startup process
recovering 0000000100000EA9000000A6 
    
•    postgres=# SELECT * FROM pg_stat_activity; 
server closed the connection unexpectedly 
        This probably means the server terminated abnormally 
        before or while processing the request. 
The connection to the server was lost. Attempting reset: Succeeded. 
 
•    Connections got normal after successful recovery: 
214847 | jiradb_7_0_10 | 31453 |    16385 | jirauser |                  |
172.28.50.226 |                 |       57530 | 2019-08-20
00:33:54.444258-05 | 
                 | 2019-08-20 00:36:57.03654-05  | 2019-08-20
00:36:57.276092-05 | f       | idle                |             |
   | SELECT COUNT(I.ID) FROM 
public.jiraissue I WHERE I.PROJECT=$1 
214847 | jiradb_7_0_10 | 31667 |    16385 | jirauser |                  |
172.28.50.226 |                 |       57632 | 2019-08-20
00:35:42.319525-05 | 2019-08-20 00 
:36:58.355277-05 | 2019-08-20 00:36:58.355307-05 | 2019-08-20
00:36:58.355308-05 | f       | active              |             |
1672613460 | INSERT INTO "artstatemap 
" (issueid, stateid, year, month, day) SELECT issueid, stateid, $1, $2, $3
FROM "artstatemap" WHERE year=$4 AND month=$5 AND (day = $6) AND (issueid >=
$7 AND issueid < 
= $8) 
214847 | jiradb_7_0_10 | 31549 |    16385 | jirauser |                  |
172.28.50.226 |                 |       57576 | 2019-08-20
00:34:44.761641-05 | 
                 | 2019-08-20 00:36:57.363577-05 | 2019-08-20
00:36:57.363587-05 | f       | idle                |             |
   | COMMIT 
  13003 | postgres      | 31672 |       10 | postgres | psql             |
            |                 |          -1 | 2019-08-20 00:35:43.673998-05
| 
                 | 2019-08-20 00:35:48.573473-05 | 2019-08-20
00:35:48.720062-05 | f       | idle                |             |
   | SELECT d.datname as "Nam 
e",