ORA-01145: offline immediate disallowed unless media recovery enabled

I faced this error while I was trying to take a datafile offline and my database was in mount state as well as in noarchivelog mode, at that time. Opening database would return ORA-01157 for this datafile.

SQL> alter database datafile 'd:\oracle\oradata\data01.dbf' offline; alter database datafile 'd:\oracle\oradata\data01.dbf' offline * ERROR at line 1: ORA-01145: offline immediate disallowed unless media recovery enabled

Creating Standby Database using Duplicate from Active Database

I already have articles written about how to create dataguard and creating dataguard in RAC environment. I used the DUPLICATE DATABASE command using backup, to build the standby database in aforementioned documents. In this article I would provide some tips about building standby database using DUPLICATE with ACTIVE DATABASE option.
Please also refer to this article about duplicate using ACTIVE DATABASE.

Follow all steps same as mentioned in how to create dataguard to build the standby, but remember following points/steps.

Slow tnsping Response and Slow Connections to the Database

We can use TNSPING utility to check connection with the database, for the client side. If you observe that TNSPING is returning very late/slow, and application connection is also very slow, there are a couple of things that you can check. First thing is to use network speed. You can use OS command “ping” to check if network is stable and response is fast enough. You can also seek help of your network team to verify if network is working as expected, and no latency or packet loss is being observed.

ORA-12170 : TNS:Connect timeout occurred

If your application (or SQLPLUS) is returning ORA-12170 while connecting to the database, there are a few things that you can verify in order to find out the root cause of the issue, and implement a solution. Although sometimes it is quite difficult to find out the root cause, I will discuss some major and quite common causes of this error message that cause failure of application to connect with the database.