When I try to connect to Oracle database from the remote host (I use oracle instant client), I get following errors:

```
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3640
Additional information: 1108778635
Process ID: 0
Session ID: 0 Serial number: 0

```

However, `ORACLE_HOME` on the host machine is set correctly, as well as `ORACLE_SID`, and i can easily connect to the database from its host machine:

```
SQL*Plus: Release 12.1.0.2.0 Production on Wed Jul 10 09:20:09 2019

Copyright (c) 1982, 2014, Oracle.  All rights reserved.

Enter user-name: system
Enter password:
Last Successful login time: Wed Jul 10 2019 09:13:57 +03:00

Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

```

What can cause this sort of behavior?
UPD:
Status of the listener on the remote DB:

```
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=192.168.71.2)(PORT=1521)))
STATUS of the LISTENER
------------------------
Alias                     LISTENER
Version                   TNSLSNR for Linux: Version 12.1.0.2.0 - Production
Start Date                05-JUL-2019 08:56:16
Uptime                    6 days 23 hr. 29 min. 47 sec
Trace Level               off
Security                  ON: Local OS Authentication
SNMP                      OFF
Listener Parameter File   /u01/app/oracle/product/12.1.0/dbhome_1/network/admin/listener.ora
Listener Log File         /u01/app/oracle/product/12.1.0/dbhome_1/log/diag/tnslsnr/epyc-gbu2/listener/alert/log.xml
Listening Endpoints Summary...
  (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=192.168.71.2)(PORT=1521)))
  (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC1521)))
Services Summary...
Service "AGRO.GBUBDD.RU" has 1 instance(s).
Instance "AGRO", status UNKNOWN, has 1 handler(s) for this service...

```

UPD2:
The command I use to connect to remote DB:

```
sqlplus /nolog
connect system/oracle@192.168.71.2:1521/agro.gbubdd.ru

```