CL_DMC_RTO_ACS_CALC_INDEXCLUST - MWB runtime object cluster fill + acc.pl.calc (server)

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The methods of this class are used to generate a function module that selects the data to be transferredin the sender system and stores them in a cluster table (INDX-type table). As in the normal access plancalculation, these data are subdivided in data portions of a predefined block size. For each data portion,a cluster entry is created. In table DMC_ACCESS_PLAN, for each data portion an entry is created. Here,instead of defining a portion delimitation by means of certain values of the portioning field, the IDof the respective cluster entry is stored. In addition, runtime information is created in the same way as in the access plan technique.

The generated access plan calculation / cluster fill function modules deal with two additional tables, compared to the usual access plan calculation function modules:

1. Assignment table DMC_CLUPTR, which assigns to a combination of conversion object identifier and access plan identifier a cluster pointer.
2. The INDX-type table DMC_INDXCL which stores the data to be transferred. For each conversion object andaccess plan, a certain number range is reserved for the IDs of the corresponding cluster records. Theoffset needed to calculate the IDs of a certain object and access plan is taken from the assignment table mentioned above.

The access plan generation for cluster tables works in a very similar way as the existing access plan generation for transparent tables:

Main differences are:

• Sort order for reading the header table is not any longer the selection field which becomes irrelevant.Instead, the data are read without sorting. Advantage: We do not need to care for an individual keyfield to be sufficiently selective. Instead, each header table record along with the corresponding child table records can establish a data portion, regardless of the values of any individual key field.

• There is no need to make a portion delimitation by means of a selection field (portioning field).Instead, for each data portion, we only store the portion number and the corresponding CLUID to allow a quick access to the cluster entry during the data load.

• all the data pertaining to one portion are exported into the cluster with the corresponding clusterID. Before it is started to export data into the cluster, it is made sure that for the current combinationof conversion object and access plan, all cluster data that might have been written to the cluster beforein former load processing are cleared. For this purpose, a new function module DMC_DEL_CLUSTER_DATA was created.

Exporting tables EX_IT_RECCOUNTS and EX_IT_TABWIDTHS are returned as in the access plan generation for transparent tables.

As in the customary access plan calculation, it is possible to only test the selectivity of the key fields, so for this purpose, the methods of this class generate the same coding.

The access plan calculation module can also be used (in the TDMS scenario) to merely provide informationconcerning the data volume that would need to be transferred. In this case it is not necessary to putthe data into the cluster. Therefore the filling of the cluster data is dependent on an additional input parameter of the function module.

The main method of this class is the GENERATE method which calls the other methods to perform subtasksof the gneration, such as selectivity determination, cursor definition, check for blocksize limit reached, creation of a new data portion, etc.

When selecting the header table data, it is possible to control, by means of a database hint, that afull table scan should be performed, rather than using an index. This is better if no appropriate indexis available, or if a considerable share of the data are to be processed. Depending on a parameter passed to the generate method, this database hint is generated or not.

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