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Alternative Space MAP page size depending on contention

IP.com Disclosure Number: IPCOM000239942D
Publication Date: 2014-Dec-17
Document File: 5 page(s) / 227K

Publishing Venue

The IP.com Prior Art Database

Abstract

A space map page identifies the data pages that have enough free space for additional data to be inserted. Currently, SMAP is defined in the DDL, and all the table space should use the same size. This article would introduce a new mechanism for alternative Space MAP page size. When the contention on a SMAP, we would split the SMAP into two. It would help to reduce the contention on SMAP to enhance the data change performance. Data change include record INSERT, UPDATE and DELETE.

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Page 01 of 5

Alternative Space MAP page size depending on contention

A space map page identifies the data pages that have enough free space for additional data to be inserted. Each space map in a page set covers a specific range of pages; the size of the range is computed on the basis of the type of page set (segmented file, non-segmented file, partitioned file, LOB, or index), the page size, and whether the page set has the MEMBER CLUSTER attribute. There are six corresponding space map page formats: segmented, non-segmented, partitioned, LOB high-level, LOB low-level, and index. Non-segmented and partitioned file page set space map pages are almost identical and are therefore described together in this section.

Currently, SMAP is defined in the DDL, and all the table space should use the same size. When the data pages which are very near to each other changes frequently, the database might repeatedly set latches on the same SMAP. It would cause page contention dramatically, and page latches contention is one of the most problems which affect the database performance.

We would like to introduce a new mechanism for alternative Space MAP page size. When the contention on a SMAP, we would split the SMAP into two. It would help to reduce the contention on SMAP to enhance the data change performance. Data change include record INSERT, UPDATE and DELETE.

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In out invention, we would like to dynamically split SMAP depending on the latch contention. As the following example,

We could issue this feature as setting special register (DYNBAMIC_SAMP). We should also define a threshold in PARM, when contention is over the threshold, the system could divide the SMAP into two by half or interval as following graph. We calculate it by the insert sequential when contention occurs. If the insert row are sequential in order, the system w...