The algorithm works by eliminating duplicate values within a database block, even across multiple columns. Compressing securefile columns have different syntax, syntax that specifiles compression within the LOB clause. Basic and Advanced compression are installed by default without the need of explicitly selecting the component for install during the installation of the Oracle Database Server, or creation of the database. select segment_name, segment_type, bytes/1024/1024 MB from user_segments where segment_type='TABLE' and segment_name='DV_XXXXXX_HST'; --- 4341 (Size in MB before COMPRESSION) Then we compressed the table for OLTP using. When a table is set to use OLTP compression and rows are inserted into a new block in that table they are inserted uncompressed, just as with a non-compressed table. Basic compression comes with oracle 11g Enterprise Edition, To make table as OLTP compressed its again extra cost option with … Oracle Database attempts to compress data during direct-path INSERT operations when it is productive to do so. * When you enable table compression by specifying either COMPRESS or COMPRESS BASIC, you enable basic table compression. Classes, workouts and quizzes on Oracle Database technologies. Compressed blocks contain a structure called a symbol table that maintains compression metadata. The original import utility (imp) does not support direct-path INSERT, and therefore cannot import data in a compressed format. All subsequent (aka normal) DML will not create compressed data. In the above explanation can you mention why was the blocks space not got released even though the table is compressed what could be done to release the blocks, Is this answer out of date? Enhancement has been logged to request the possibility to disable/un-install the option. * When you enable table compression by specifying COMPRESS FOR OLTP, you enable OLTP table compression. Expertise through exercise! OLTP Table Compression reduces the associated compression overhead of write operations making it suitable for transactional or OLTP environments as well. This document is focused solely on OLTP Compression which is one of several types of heap segment compression (HSC), the other features of the Advanced Compression Option as listed above are not covered here. You can also catch regular content via Connor's blog and Chris's blog. OLTP Table Compression is a part of the Oracle Advanced Compression option, which requires a license in addition to the Enterprise Edition. You will get no compression benefits from conventional path inserts, updates or deletes. This form of compression is recommended for OLTP environments. ” Oracle’s OLTP Table Compression uses a unique compression algorithm specifically designed to work with OLTP application. We’ll do the same again, but use the option “compress for OLTP” (or “compress for all operations” for those using a slightly older version of Oracle). And of course, keep up to date with AskTOM via the official twitter account. Compress = compress data *only* during direct mode operations (sqlldr, ctas, insert-append, alter table move). As the name implies, this option enables compression for all operations, including regular DML statements. ALTER TABLE DV_XXXXXX_HST MOVE COMPRESS FOR OLTP; checking the size of the table after compression. It is designed for use with direct path loads only. Basic compression is not designed for OLTP operations. My Oracle Support provides customers with access to over a million knowledge articles and a vibrant support community of peers and Oracle experts. Answered by: Connor McDonald - Last updated: August 16, 2017 - 11:58 am UTC. Connor and Chris don't just spend all day on AskTOM. If a table contains LOB columns then it is possible to compress table only  without compressing the LOB data. Or if video is more your thing, check out Connor's latest video and Chris's latest video from their Youtube channels. Share and learn SQL and PL/SQL; free access to the latest version of Oracle Database! For more details see Document 1459216.1. OLTP Table Compression, therefore, extends the benefits of compression to all application workloads. Oracle Database compresses data during all DML operations on the table. Create table as select from all_obje… Basic compression is a free option with the Enterprise Edition version of the database.