Compression and Smart Blobs
IDS 11.50.FC5 AIX 5.3 (4K Page Size) Smart blobs here default to 4k dbspaces (not allowed to specify a size when creating the smart blob space). From Admin Guide, page 10-48: Dynamic Server can compress any combination of data types, because it treats all data to be compressed as unstructured sequences of bytes. Thus, the server can compress patterns that span columns, for example, in city, state, and zip code combinations. (Dynamic Server uncompresses a sequence of bytes in the same sequence that existed before the data was compressed.) There are no restrictions on the types of data that can be compressed. Compression is applied only to the contents of data rows, including any remainder pieces for rows that span pages, and the images of those rows that are contained in logical log records. Many types of large-object data (such as images and sound samples) in rows might already be compressed, so compressing the data again would not achieve any additional saving of space. From Admin Guide, page 10-49: If XML data is stored with the first portion in a row and the remainder outside of the row, compression is only applied to the portion that is stored in the row. My Questions: If I compress a table that contains a CLOB (stored within a smartblob using the PUT option of CREATE TABLE), is the data contained with the smart blob also compressed? What about XML stored in a CLOB? Or would it just compress the first 4k of the XML and stored uncompressed any reminder? Thanks in advance. Clifton _________________________________________________________________ Hotmail: Trusted email with Microsoft's powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ http://clk.atdmt.com/GBL/go/177141664/direct/01/
ids-bounces@iiug.org wrote on 11/18/2009 07:48:10 AM: > From: > > "Clifton Bean" <clifton_bean@hotmail.com>: > > To: > > ids@iiug.org > > Date: > > 11/18/2009 07:49 AM > > Subject: > > Compression and Smart Blobs [18146]. > > Sent by: > > ids-bounces@iiug.org > > IDS 11.50.FC5 AIX 5.3 (4K Page Size) > > Smart blobs here default to 4k dbspaces (not allowed to specify a size when > creating the smart blob space). > > >From Admin Guide, page 10-48: > > Dynamic Server can compress any combination of data types, because it treats > all data to be compressed as unstructured sequences of bytes. Thus, > the server > can compress patterns that span columns, for example, in city, state, and zip > code combinations. (Dynamic Server uncompresses a sequence of bytes in the > same sequence that existed before the data was compressed.) > > There are no restrictions on the types of data that can be compressed. > > Compression is applied only to the contents of data rows, including any > remainder pieces for rows that span pages, and the images of those rows that > are contained in logical log records. > > Many types of large-object data (such as images and sound samples) in rows > might already be compressed, so compressing the data again would not achieve > any additional saving of space. > > >From Admin Guide, page 10-49: > > If XML data is stored with the first portion in a row and the remainder > outside of the row, compression is only applied to the portion that is stored > in the row. > > My Questions: > > If I compress a table that contains a CLOB (stored within a smartblob using > the PUT option of CREATE TABLE), is the data contained with the smart blob > also compressed? > > What about XML stored in a CLOB? Or would it just compress the first4k of the > XML and stored uncompressed any reminder? Answer to both questions is NO. IDS compress "in-row" data only. IDS will compress the large object descriptor which is stored within the row. Actual CLOB data (stored out-side of the row in a smart blob space) won't be compressed. - Nilesh - > > Thanks in advance. > > Clifton > > _________________________________________________________________ > Hotmail: Trusted email with Microsoft's powerful SPAM protection. > http://clk.atdmt.com/GBL/go/177141664/direct/01/ > http://clk.atdmt.com/GBL/go/177141664/direct/01/ > > > ******************************************************************************* > Forum Note: Use "Reply" to post a response in the discussion forum. >