Exp/imp under Oracle

In peacetime to do backup of Oracle is usually to do a logical hot backup, and do a logical hot backup is generally used Exp/imp, here is simple to say.

Export Data using EXP IMP import data operation as follows:

Exp Username/password owner=backup file=backup.dmpimp username/password file=backup.dmp ignore=y full=y

Explain here that ignore=y means ignoring the creation error and continuing with the subsequent operation, which in full=y means that all imports include table constraints, which is important when importing.

However, one thing to note here is that after the beginning of the Oracle 11g version, a new feature is added when the table has no data, the segment is not allocated to save space, and the lack of this feature is turned on and can be viewed in the following ways:

Sql> Show parameter deferred_segment_creation;

Therefore, after the 11g version to use EXP export also need to do the appropriate check, of course, because this feature makes the 11g version when using EXP export encountered empty table will not be exported, this problem has a lot of solutions, of course, the personal more acceptable method should be closed before export deferred_ The Segment_creation function then checks all empty tables and then allocates space for all the empty tables found, as follows:

Sql> alter SYSTEM SET deferred_segment_creation=false;sql> SELECT table_name from user_tables where num_rows=0;sql > select ' ALTER TABLE ' | | table_name| | ' allocate extent; ' from User_tables where num_rows=0

At this point, you can export with exp

This article from the "Technical essay" blog, reproduced please contact the author!

Exp/imp under Oracle