size of tbs

I donot understand your question correctly, you are saying that you have 2GB tablespace available and 4GB data needs to be imported, but there is no space in mount point. Correct?
How did you calculated 4GB? If you are referring to existing tablespace size, then actual space needed might not be 4GB.
If you are referring that Table size is 4GB, then again actual data might be lesser than object size.
If you are referring flat file size of 4GB, then you need more than 4GB in Oracle.

That means there is no space now in the tablespace..


Big data is coming..

Try tablespace compression.
Please go through below document http://www.dba-oracle.com/oracle11g/sf_Oracle_11g_Data_Compression_Tips_for_the_DBA.html

@virdi If the tablespace is full and cannot extend, for whatever reason, how would compression manage the temporary storage needed?  I don't know.

@Tony, does your storage system have physical space available for the tablespace to expand?  I infer not from "no space in the mount point".

Can your SA not allocate additional storage for your datafiles?

Have you explored what caused the existing storage to fill up, apparently undetected?

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