Decrypting an Existing Tablespace with Offline Conversion

To decrypt an existing tablespace with online conversion, you can use the ALTER TABLESPACE SQL statement with DECRYPT clause.

1. Login to DB instance as a system user.

SQL> connect system/<password>; 

2. List encrypted tablespace.

SQL> select TABLESPACE_NAME, ENCRYPTED from DBA_TABLESPACES; 

3. Open a Keystore.

SQL> ADMINISTER KEY MANAGEMENT SET KEYSTORE OPEN IDENTIFIED BY <hsm_password>;

4. Bring the tablespace NONSECURE01_TS offline.

SQL> alter tablespace NONSECURE01_TS OFFLINE NORMAL;

5. Decrypt the existing tablespace NONSECURE01_TS.

SQL> alter tablespace NONSECURE01_TS ENCRYPTION OFFLINE DECRYPT; 

6. Bring the tablespace NONSECURE01_TS online.

SQL> alter tablespace NONSECURE01_TS ONLINE; 

7. Verify the tablespace got decrypted.

SQL> select TABLESPACE_NAME, ENCRYPTED from DBA_TABLESPACES;