Null takes 1 bytes. About licensing, nocompress is availaible in all editions: This is the compression that we know as COMPRESS since 9i. Nous proposons nos clients des solutions adaptes et sur mesure grce nos consultant.e.s dont les comptences et connaissances voluent constamment grce la formation continue.
TEST_STR_50 has 49 random character strings with any printable characters low duplicate probability, TEST_NUM_05 and TEST_NUM_22 are integer and decimal numbers from 1 to one million, TEST_DAT_08 is all different dates and TEST_DAT_V8 has only 5 distinct dates. This compression is not suited for updates. dbi services est une entreprise spcialise dans le consulting et les services IT. And that locking feature is licenced with the Advanced Compression Option, and available in Exadata only. 
Note that this is not a technical choice but a maketing one. The gain in I/O (because of the reduced size) compensates the CPU overhead to decompress. In this exemple, I dont get an higher ratio, but that depends on data pettern. Compression ratio is good especially when we have a lot of repeated values. Then, without it, you can use only the BASIC COMPRESSION. Note that I dont know why HCC is not flagged by feature usage here. In QUERY levels its suited for data that read frequently. About licensing, COMPRESS BASIC is availaible in Enterprise Edition only, but without any option: Because basic compression is not available for OLTP with conventional DML, 11g introduced the same compression but automatically triggered when a block becomes full. This is always possible in Enterprise Edition.
If you have an Oracle storage, then you can use the EHCC compression. Anyway COLUMN STORE compression can be transformed to ROW STORE compression during updates. It about the same compression ratio as the basic compression: But it is licenced as an additional option: Advanced Compression Option: Note that in 12c a lot of features has been introduced as part of ACO. In 12c the syntax for higher ZLIB level is: COMPRESS FOR ARCHIVE LOW. In 12c you have the ADO (Automatic Data Optimization) option to compress automatically cold data. If you want to do it automatically the A of ADO you need to buy ACO option. The only compression that happens is that nulls at the end of rows are not stored. As soon as there is an update the block is decompressed. .
In 12c the syntax is: COLUMN STORE COMPRESS FOR ARCHIVE HIGH, This level is better, but requires lot of CPU both to compress and uncompress.
The full syntax is: ROW STORE COMPRESS ADVANCED. No need to schedule regular reorganization to compress the blocks that are full. It is a block compression where duplicate values are not repeated: the value is put in the block header and each column has only a pointer to it. (COMPRESS ADVANCED is not needed here because ADO does bulk loads anyway). There are 4 levels. Name change for technical reasons (ROW/COLUMN STORE precision when a columnar compression has been introduced) or for marketing reason (COMPRESS FOR OLTP gave the idea that other Exadata compression level may not be suited for OLTP). Various methods of table compression have been introduced at each release. But not in ODA. When do you need ACO (Advanced Compression Option) or not? This does not need additional option when you do it manually. 12c removed the FOR OLTP and named it with the name of the option.
In 12c the syntax is: ROW STORE COMPRESS BASIC. Then compression must be done manually and you will probably use ALTER TABLE MOVE PARTITION COMPRESS BASIC ONLINE. Nous sommes des experts des infrastructures et plateformes de donnes innovantes et efficientes. Ill only show the 12c syntax here and the compression obtained on the previous table: In 12c the syntax is: COMPRESS FOR QUERY LOW. But once again the EHCC is available only for Oracle storage. Those EHCC are available in Oracle supplied storage: Exadata database machine, Oracle SuperCluster , ZFS storage appliances, Pillar axiom array. Here I dont have a lot of duplicates for large columns, so the compression ratio is not very good. Reading row-by-row from any COLUMN STORE is not very efficient, especially when we need to decompress the whole compression unit.
Its suited for DML operation but is different than FOR OLTP. Without ACO option you cannot use it. The compression library is in the Oracle database binaries and the feature availability is enabled depending on storage type (visible through SNMP). Deduplication is not only for same column. In ARCHIVE mode the CPU usage makes it no optimal for queries, so its only for non-frequently accessed data. That compression occurs only when filling full blocks with bulk load (direct-path load, insert append). And its not always very clear for the simple reason that their name has changed. Multiple blocks are grouped into Compression Unique where table data is stored in column. One important thing to know is that even in QUERY levels its optimized for bul reads. You can use Automatic Data Optimization for ILM only with that option even if you dont compress and ieven if you compress it is not an ADVANCED COMPRESS. db-crawler, a database search utility for Documentum, HCC is called COLUMN STORE even if it has nothing to do with the In-Memory columns store, COMPRESS ADVANCED is only one part of Advanced Compression Option, EHCC (Exadata Hybrid Columnar Compression) is not only for Exadata, COMPRESS FOR OLTP is not called like that anymore, but is still the only compression suitable for OLTP, HCC Row-Level Locking is not for ROW STORE but for COLUMN STORE. So the Advanced in Advanced Compression Option rather mean Automatic when related to ILM, Encore un bilan la hausse pour dbi services, Eine weitere Umsatzsteigerung fr dbi services. Some are only for static data. Im created a few tables storing characters, numbers and dates: Here is the size in blocks (blocks are 8k). TEST_STR_A4 has 3 random character strings, TEST_STR_U4 has the same but only uppercase (so more duplicates). The compression levels are detailed by @KovachevPro in theprogeekingblog. Then a compression algorithm is applied.
Of course that brings a lot of ambiguity such as: In NOCOMPRESS the default each datatype takes its full length. Some require a specific storage system Some requires specific options. Probably a bug in catfusrg.sql but anyway you dont need to buy license for that just by your storage at Oracle. Number takes about 2 significan digits per bytes, dates takes 8 bytes, characters string takes one byte (or more in multibyte charactersets) per character, plus the length. Exadata introduced Hybrid Columnar Compression.