The 20c Database Upgrade Mystery

Oracle Database 20c is available only for preview. It is not available for production use. Upgrades to or from Oracle Database 20c are not supported.

So, upgrades are not supported but there exists an Oracle Database 20c Upgrade Guide. The 20c upgrade pdf file is 461 pages long!

Let me shed some light on this “mystery”.

As of today, April 27th 2020 (Oracle Database 19c is today 1 year old on Linux), Oracle 20c is only available from the Oracle Public Cloud in preview mode. To try out this 20c preview, you will need an Oracle Public Cloud tenancy with cloud credits (paid or promotional), as the DBCS instance will require an OCI Compute VM. And, by the way, 20c does *not* run on Exadata.

Once 20c becomes generally available also in non-preview only mode, upgrades will be also available.

You can perform a direct upgrade to the new release from the following releases:

• 19c
• 18c
• 12.2.0

Here is what we need to know about compatibility:

– Before upgrading to Oracle Database 20c, you must set the COMPATIBLE initialization parameter to at least 12.2.0
– In Oracle Database 20c, when the COMPATIBLE initialization parameter is not set in your parameter file, the COMPATIBLE parameter value defaults to 20.0.0
– Installing earlier releases of Oracle Database on the same computer that is running Oracle Database 20c can cause issues with client connections

The most important point about the 20c architecture is that starting with the first release of Oracle Database 20c, non-CDB Oracle Database upgrades to non-CDB architecture are desupported. Meaning you need a container and your data will be in a pluggable database.

Starting with Oracle 19c you can have up to 3 pluggable databases (PDBs) per container database (CDB) without requiring additional multitenant license. See page 11 of Oracle Database Licensing Information User Manual for all the details (it is a 361 page pdf file).

So, when upgrading to 20c, we have 2 options:

Option 1: Convert the non-CDB to a PDB before upgrade

With this option, you plug in the non-CDB Oracle Database release to the same release CDB. For example, plug in a non-CDB Oracle Database Release 19c into an Oracle Database 19c release CDB. Finish converting the non-CDB Oracle Database to a PDB. Then, upgrade the entire CDB, with its PDBs, to Oracle Database 20c.

Option 2: Plug in the non-CDB, upgrade, and finish converting the non-CDB to a PDB after upgrade

With this option, you plug in a non-CDB Oracle Database release to an OracleDatabase 20c CDB. Upgrade the plugged-in non-CDB Oracle Database to Oracle Database 20c. Then, finish converting the non-CDB Oracle Database to a PDB.

Here is what you need to know about the DBUA and the Oracle home:

– Starting with Oracle Database 20c, Database Upgrade Assistant (DBUA) is replaced by the AutoUpgrade utility
– Starting with Oracle Database 20c, the default network administration directory changes from the previous default in the local Oracle home, Oracle_home/network (for example, /u01/app/oracle/product/19.1.0/dbhome_1/network), to a new location.
– The new default location is the shared Oracle Base Home, in the path ORACLE_BASE/ homes/HOME_NAME/network/admin
– Starting with Oracle Database 20c, an Oracle Database installation configures all Oracle Database homes in read-only mode by default

And here is what you need to know before the upgrade about security and the init.ora parameters:

– Starting with Oracle Database 20c, the data types DBMS_CRYPTO_TOOLKIT_TYPES and package DBMS_CRYPTO_TOOLKIT are desupported
– The init.ora parameters UNIFIED_AUDIT_SGA_QUEUE_SIZE, UNIFIED_AUDIT_SGA_QUEUE_SIZE, AUDIT_FILE_DEST, AUDIT_SYS_OPERATIONS, AUDIT_SYSLOG_LEVEL an d AUDIT_TRAIL have been desupported
– Desupport of IGNORECASE parameter for passwords: starting in Oracle Database 20c, the IGNORECASE parameter for the orapwd file is desupported and all newly created password files are case-sensitive
– Desupport of DISABLE_DIRECTORY_LINK_CHECK: the DISABLE_DIRECTORY_LINK_CHECK parameter is desupported, with no replacement

Further info and links were listed in detail by the King of Database Upgrades Mike Dietrich – his blog is dedicated to Oracle Database upgrades!

Now, how about long term support? Do you care only about LTS database releases when planning upgrades? As Tim Hall says: “It’s important to check out what is happening in the 20c release, because it may alter how you use the earlier releases now. There is no point launching into a new development using a feature that is about to disappear. Remember Oracle Streams anyone?” Yes, indeed Tim: Streams, Advanced Replication… I rather be on the latest release and use the new features – live and learn…

Tablespaces in Oracle Database 20c

Oracle 20c, released recently with 138 new features, is still only available from the cloud but it brings one major change for DBAs which they can no longer avoid: use containers and pluggable databases. And this changes slightly the way how DBAs look also at tablespaces.

But what is new in 20c about tablespaces? Now, DBAs can set the default tablespace encryption algorithm:

The new TABLESPACE_ENCRYPTION_DEFAULT_ALGORITHM dynamic init.ora parameter defines the default encryption algorithm for tablespace creation operations. The default value in 20.2.0 is AES128.

If you set TABLESPACE_ENCRYPTION_DEFAULT_ALGORITHM to say 3DES168, then all future tablespace creation operations will use 3DES168 as the default encryption algorithm. And this is both for offline and online tablespace encryption operations.

The supported values for the encryption algorithms are AES128, AES192, AES256, ARIA128, ARIA192, ARIA256, GOST256, SEED128 and 3DES168.

The CREATE TABLESPACE command in 20c is not more complex than before. Tablespaces can be permanent, undo or temporary; bigfile (one data file or temp file up to approx. 4 billion blocks, max. size is 128 terabytes (TB) for a tablespace with 32K blocks and 32TB for a tablespace with 8K blocks) or smallfile (max. 1022 data files or temp files each with max. 4 million blocks).

The concept of tablespace sets is not new but not highly adopted.

But going back to tablespaces and PDBs. Here is the output from DBA_TABLESPACES run from a PDB as SYS:

And here is the the output from DBA_TABLESPACES run from the root container as SYS:

Of course, DBA_TABLESPACES is no longer the place from which the DBA will find all tablespaces from the database. The correct one is CDB_TABLEPSPACES but if you run the “select * from cdb_tablepsaces;” as SYS from within the PDB, you will still get the same output.

However, run is as SYS from the root container, you get what you are looking for:

From 20c onwards, DBA should get used to the new CDB_ views. And then, less and less people will ask the question “Why do we have 2 tablespaces with the same name?”….

Here is something else which is new in 20c: Oracle automatically shrinks an Oracle ACFS file system based on policy providing there is enough free storage in the volume. ACFS stands for Automatic Storage Management Cluster File System.

In 20c, you can use now File Group templates by customizing and setting default file group properties for automatically created file groups. Without file group templates if you wanted to change properties for an automatically created file group you would have to manually change the properties after the associated files are created which triggers an unnecessary rebalance. The file group templates feature provides a much better option.

New is also the SecureFiles defragmentation, it provides online defragmentation of allocated and freed space in SecureFiles segments for all types of SecureFiles LOBs – compressed deduplicated encrypted. Defragmentation can be done automatically by a background process and the segment advisor can estimate the fragmentation levels and how much space can be saved. Defragmentation can be done mostly in-place with some temp segment space needed to hold intermediate results.

Next, there are 2 new features of Data Pump related to tablespaces:

– Starting with Oracle Database 20c, Data Pump improves transportable tablespace metadata operations with parallelism. Oracle Data Pump now supports parallel export and import operations for Transportable Tablespace (TTS) metadata. This is the information that associates the tablespace data files with the target database in a TTS migration. Parallelism improves TTS export and import performance especially when there are millions of database objects in the data files including tables indexes partitions and subpartitions.

– Starting with Oracle Database 20c, Data Pump resumes transportable tablespace export and import jobs that are stopped. Oracle Data Pump has the capacity to resume transportable tablespace export and import jobs. Due to errors or other problems you can find that transportable tablespace export or import jobs are stopped. Oracle Data Pump’s capacity to resume these stopped jobs helps to save you time and makes the system more available.

Another new 20c feature is Automatic Zone Maps which are created and maintained for any user table without any customer intervention. Zone maps allow the pruning of blocks and partitions based on the predicates in the queries without any user intervention. Automatic zone maps are maintained for direct loads and are maintained and refreshed for any other DML operation incrementally and periodically in the background. Automatic zone maps are improving the performance of any query transparently and automatically without the need of any user action. However, this feature is available only on Exadata.

And finally, something which I find interesting in the good way: starting with Oracle Database 20c, you can specify an expression as the value for some initialization parameters, which enables the database to automatically adjust the parameter value in response to environmental changes. This is especially useful in Oracle Autonomous Database environments.

Example: CPU_COUNT = $SYSTEM_CPU/4 or SESSIONS = MAX(200, PROCESSES * 1.5)