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## Usage considerations 

The removal of log force write for identity columns and XML DOCID columns in a Db2 12 data sharing environment is automatically enabled when Db2 is at function level V12R1M100 and greater. No special configuration is required to use this enhancement. 

Note:  This enhancement does not apply to sequences. 

## 2.5 Range-partitioned table spaces with relative page numbering 

Before Db2 12, the maximum partition size is limited to 256 GB. In cases when the partition size is 256 GB, a maximum of 64 partitions is allowable for table spaces that use a 4 K page size. Although the maximum number of partitions is 4096, the actual maximum number of partitions a table can have is determined by its partition size and its page size. This limitation exists because pages are numbered sequentially at the table space level and the partition number of a data page is implicitly imbedded in the first n  bits (where n  depends on the number of partitions) of its page number. 

In Db2 12, a new type of partition-by-range universal table space is introduced. This new type of range-partitioned table space uses relative page numbering where the page numbers start from zero at the partition level. Pages are no longer absolute page numbers in the table space. This new type of table space is called Partition-By-Range - Relative Page Numbering (PBR RPN). 

PBR RPN table spaces can have a maximum partition size of 1 TB. The maximum number of partitions continues to be up to 4096 partitions, which means the maximum size of a PBR RPN table space is 4 Petabytes (4 PB) with 4096 partitions. The number of partitions is no longer dependent on the partition size. PBR RPN table spaces also allow certain attributes, such as DSSIZE, to be specified at the partition level instead of the table space level. 

To enable this partition-independent page numbering, the size of a Record ID (RID) is expanded to 7 bytes. Internally, Db2 always uses the new 7-byte RIDs. As a result, longer log records are created in Db2 12, regardless of whether PBR RPN table spaces are used. Log records that are related to table spaces and indexes increase by 20 bytes. 

Range-partitioned table spaces with relative page numbering can be created in Db2 12 at function level V12R1M500 and beyond only. A new system parameter called PAGESET_PAGENUM is also introduced by this enhancement. It controls whether page numbering of newly created PBR table spaces is relative or absolute by default. The default setting for the parameter is to use absolute page numbering (this setting is to have the same behavior as in previous Db2 versions). 

