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Partitioning the LOB storage structures z/OS DFSMS OAM Planning, Installation, and Storage Administration Guide for Object Support SC23-6866-00 |
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During OAM installation and customization (using the default SAMPLIB
members provided with the product), OAM creates a nonpartitioned unique
clustered index on the LOB storage structure using a composite key
consisting of both:
You might change the DB2 table space containing the LOB storage
structure into a partitioned table space. If you do so, decide which
column or columns on the LOB storage structure to use for the partitioning
key. The following two examples of columns in the LOB storage structure
might be used for the partitioning key:
OAM does not update the value of the collection ID column (OTCLID) in a row in the LOB storage structure, so this column might be used in a partitioning key. OAM does not update the value of the object name column (OTNAME) in a row in the LOB storage structure, so this column might be used in a partitioning key. If you use the object name column (OTNAME) as the partitioning key, remember that DB2 only uses the first 40 bytes of the partitioning key to actually partition the data. Another option to partition the LOB storage structure is by adding a column that you use only as the partitioning key.
To create the DB2 table space containing the LOB storage structure as a partitioned table space, you must modify the CREATE TABLESPACE SQL statements by adding a NUMPARTS clause for the HLQ.OSMLBTS and table spaces in the CBRILOB job in SYS1.SAMPLIB. If you create the DB2 table space containing the LOB storage structure as a partitioned table space, you must define a partitioned index on the LOB storage structure. The partitioned index can be created by adding a CREATE INDEX SQL statement to the CBRILOB sample job in SYS1.SAMPLIB. If you create the DB2 table space containing the LOB storage structure as a partitioned table space, the partitioned index must also be the clustering index. Therefore, the default index that OAM creates on the LOB storage structure (HLQ.OBJT04X1) cannot be a clustering index. In this case, you must change the default index that OAM creates on the LOB storage structure (HLQ.OTLOBX1) to a nonclustered index by removing the CLUSTER keyword from the CREATE INDEX SQL statement for the HLQ. OTLOBX1 index in the CBRILOB sample job in SYS1.SAMPLIB. If you create the DB2 table space containing the LOB storage structure
as a partitioned table space, there must still be a unique nonpartitioned
index on the composite key in order for OAM to function properly that
consists of both:
Note: Having a partitioned index and a nonpartitioned
index on the LOB storage structure might diminish some of the benefits
of partitioning the LOB storage structure.
In addition to changing the SQL statements contained in the CBRILOB sample job in SYS1.SAMPLIB, also include IDCAMS (access method services) DEFINE CLUSTER commands to preallocate a VSAM linear data set (LDS) for each of the partitions that you plan on having for each partitioned table space containing the LOB storage structure associated with each object storage group. Also use the IDCAMS DEFINE CLUSTER command to preallocate a VSAM linear data set for each partition comprising the partitioned index that you plan to create. The data set names associated with each VSAM linear data set must conform to DB2 data set naming conventions as specified in the "Data set naming conventions" topic in the IBM Information Management Software for z/OS Solutions Information Center. DB2 free space search algorithms are not as efficient for partitioned table spaces as they are for segmented table spaces. As a result of partitioning the DB2 table spaces that contain the OAM LOB storage structures, you might impact the performance when small objects are being stored to the DB2 sublevel. By partitioning the DB2 table space containing the OAM LOB storage
structure, you are accepting the following responsibilities:
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