Today, the choice of the database technology is in the hands of the developers, and Open Source alternatives look appealing. Many talks and papers show the growing features of MySQL or PostgreSQL, which competes with the commercial RDBMS. But do not forget the core features that are there for decades. They may not be there, or less efficient, in those alternative solutions. Let’s show those basic features, with demos: in-place updates, cursor sharing, guaranteed disk writes, advanced materialized views, IOT, wait events, online operations,… Many were already in Oracle 30 years ago and we take them for granted. We may not realize what we will miss when going to another RDBMS.

1. 19 features you will miss
if you leave Oracle Database
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The demos are on YouTube:
https://youtu.be/SI6qUNv-hT8

2. Who am I?
Franck Pachot
Database Engineer at CERN
• Twitter @FranckPachot
• Medium: https://medium.com/@FranckPachot
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3. Why this presentation?
I like Oracle technology, and also Open Source alternatives
However, the shout-out is not always fair:
- new features in PostgreSQL, MySQL,
MariaDB,… are advertised a lot
- features that appeared in Oracle7
are not so exiting for marketing in 2019
but still critical for business
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4. Agenda
1. lock-free SELECT
2. fast load INSERT
3. in-place UPDATE
4. index only access
5. no need to reorg
6. cursor sharing
7. partitioning
8. optimizer features
enable
9. hints
10. crash/media recovery
11. RMAN
12. My Oracle Support
13. wait Events
14. upgrade and migration
15. multiplatform
16. materialized views
17. flashback
18. Data Guard
19. … many more
20. … even more?
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5. 1. Lock-free SELECT
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You can read
• consistent data (no dirty read)
• without any lock acquired
• from any point in time
- current committed data
- recent version within UNDO_RETENTION
- past modification within FLASHBACK DATA ARCHIVE policy
No need to replicate, snapshot, archive, add timestamps with
triggers,… for reads, reporting, exports,…

6. 2. Direct-Path INSERT
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Fast load to append rows at the end of a table (or partition)
• writes pre-built blocks
• minimal UNDO, minimal REDO
• no buffer cache overhead
• no space management overhead
• no row-by-row index maintenance
For DWH load, migrations, reorganization,… or simply IoT ingestion

7. 3. In-place UPDATE
That looks simple, but PostgreSQL do not update rows
• updates are implemented as delete + insert
• which copies the whole row even if you update 1 byte
• and has to maintain all indexes because the row has moved
• and must come back to clean the old stuff after MVCC retention
Oracle minimizes the row movement:
• only when absolutely necessary (not enough space in the block)
• keeps a pointer to avoid index maintenance
• this is critical for OLTP (like update flag='Y' where flag='N')
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8. 4. Index-Only access
• Full Table Scan is good to get for lot of rows
• Table access by index ROWID is good for few rows
In-between, Oracle has a very efficient access:
• Index Access without the need to go to the table
https://medium.com/@FranckPachot/index-only-access-with-oracle-mysql-postgresql-
and-microsoft-sql-server-302383103998
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9. 5. No need to reorg
Oracle maintains the physical structures for optimal query
• with no dead tuples to vacuum
• with no visibility map to refresh
• with no unbalanced indexes
• scattered in heap by default, clustered if needed
This is important for the predictability of performance:
• no degradation over time
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10. 6. Cursor sharing
Oracle, like many commercial databases
• parse/compile/optimize the statements once
• execute the optimized plan for different sessions, on different values,…
MySQL, PostgreSQL,…
• do not share the prepared statements across sessions
Compilation is CPU intensive, no cursor sharing limits the scalability
and the possibility of advanced optimizer transformations
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11. 7. Partitioning
Storing a logical table into multiple physical one is just one step
(partition views in Oracle7). Partitioning features are:
• Partition pruning
• Partition-wise joins
• Global indexes
• Partition exchange
• Automatic creation of partitions (list, interval)
• Referential partitioning
• Thousands of partitions is not a problem.
• Completely transparent (like a table)
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12. 8. optimizer_features_enable
You can run the optimizer at any of these versions:
• 19.1.0.1, 19.1.0, 18.1.0, 12.2.0.1, 12.1.0.2, 12.1.0.1, 11.2.0.4, 11.2.0.3, 11.2.0.2,
11.2.0.1, 11.1.0.7, 11.1.0.6, 10.2.0.5, 10.2.0.4, 10.2.0.3, 10.2.0.2, 10.2.0.1,
10.1.0.5, 10.1.0.4, 10.1.0.3, 10.1.0, 9.2.0.8, 9.2.0, 9.0.1, 9.0.0, 8.1.7, 8.1.6, 8.1.5,
8.1.4, 8.1.3, 8.1.0, 8.0.7, 8.0.6, 8.0.5, 8.0.4, 8.0.3, 8.0.0
• this sets flags for all changes in the last 20 years CBO code
• + any intermediate fixes with "_fix_control"
This is key for regression troubleshooting in case of upgrade
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13. 9. Hints
Hints can apply any parameter at statement level, can prevent some
bad plans, can correct some optimizer estimations
• Full control for troubleshooting
• Base feature for SQL Plan Management
→ SQL Plan Stability
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14. 10. Crash and media recovery
When the server crashes…
Oracle:
• re-start and no worry if there are no specific errors
Many other databases:
• better verify for corruption
Did you hear about postgres fsync() and non-direct reads?
Which database can detect lost writes before it is too late?
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15. 11. RMAN
Recovery MANager
• optimizes backups (read only tablespaces, block verification)
• manages retention (recovery window, fast recovery area)
and fully manages the recovery:
• catalog: knows exactly which files are required
• recovery advisor for the most common cases
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16. 12. My Oracle Support
… any doubt about the quality of the support?
How many time a search in the Knowledge Base provided you a
solution, workaround or patch?
How many pages do you have to read to get relevant information
- vs Stack Overflow
- vs Mailing Lists
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17. 13. Wait events
Oracle is one of the best instrumented software
• all system calls are timed, with their context -> wait events
• many operations increase statistics counters
• implemented on decades of troubleshooting
- in many platforms, many applications, many workloads
No equivalent. Tracing at OS level doesn't have the context
Tkprof, Statspack/AWR, ASH, SQL real-time Monitoring…
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18. 14. Upgrade and Migrations
You can upgrade 100TB database in few hours
• no need to move data, only the dictionary is touched
You can also migrate with small downtime
• even cross-endianness
• transportable tablespace
• change characterset
• encrypt only
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19. 15. Multi-platform
Which database can you run
• on any cloud provider
• on any endianness
• on any relevant OS
without any change in your application?
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20. 16. Materialized views
It is not only a table that stores the result from a view
• Incrementally updated (Fast refresh)
• Always fresh (On-Commit and 18c real-time)
• Transparent optimization (query rewrite)
• Refresh Group: dependencies and transaction consistency
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21. 17. Flashback, FDA, LogMiner
You don't need them everyday, but they can save your job:
• restore a dropped table (flashback table)
• revert a failed application release (flashback database)
• see recently delete rows (flashback query)
• version for years without any trigger (Flashback Data Archive)
• find exactly what changed, or locked, in the past (log miner)
• …
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22. 18. Data Guard
A physical standby is the best protection:
• copies all data with minimal overhead
• on a completely different system
(vs. storage synchronization which copies also the corrupt blocks)
Data Guard
• fully automated DR (FSFO)
• transparent application failover
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23. 19…
• Online operations to save your week-ends
• Parallel Query to scale on multi-core processors
• Data Pump to copy, migrate, archive, convert,…
• Audit without any additional development
• VPD to secure and isolate data without changing the code
• CMAN to have a single network address with HA and DR
• PL/SQL, EBR, APEX… to rapidly build efficient applications
• DRCP so scale the many micro-service connection pools
• JSON support for new data with same performance and reliability
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24. 20…
One 20c feature that you will need and will not find in other databases:
Immutable table
• a table where you can insert
• but nobody can update
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Or make it more popular and call it:
CREATE BLOCKCHAIN TABLE

25. Now, the big question:
Often heard:
" We may move out of Oracle in the future, then we avoid to use
Oracle specific features as we don't want to be locked-in"
Today, you pay for Oracle, so:
• you should use the features that saves you time and money today
• if/when you move out (in years), you may find the equivalent feature
But: be sure to isolate all specifics in dedicated modules.
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26. Core message
When comparing RDBMS alternatives, look at all features.
• having similar SQL functions doesn't mean it has the same features
• the most important feature may not be the most popular buzz
• during its lifecycle the database will have to get through:
- data movement, troubleshooting, crash recovery, high concurrent activity
If the management thinks it is easy to move to non-Oracle alternatives,
try to estimate the cost (skills, time, price) for all of them.
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