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Raster datasets and raster catalogs in a geodatabase in DB2

Raster datasets and raster catalogs in a geodatabase in DB2

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Raster data is spatial data represented in an array of equally sized cells arranged in rows and columns. Raster data can be made up of one or more raster bands. For a complete explanantion of raster data and its attributes, see the "Understanding raster data" book in this help. You can start with What is raster data?

Rasters in ArcCatalog

In ArcGIS, raster data can be stored in a single raster dataset or a raster catalog. A raster catalog is a group of raster datasets. For a description of these two types of storage, see Raster data organization.

In the Catalog tree, individual raster datasets look like the following:

Raster dataset in ArcCatalog

If you expand the raster dataset, you will see the raster bands of which it is comprised.

Raster bands

A raster catalog in the Catalog tree would appear as follows:

Raster catalog

Raster tables in a DB2 DBMS

ArcSDE geodatabases in a DB2 DBMS store raster data in DB2's native binary format, which is similar to the way Oracle and SQL Server store compressed binary feature classes. A raster column is added to a business table, and each cell of the raster column contains a reference to a raster stored in a separate raster table. Therefore, each row of a business table references an entire raster.

When you import a raster into an ArcSDE geodatabase in DB2, a raster column is added to the business table of your choice. You may name the raster column whatever you like, so long as it conforms to DB2's column-naming convention. ArcSDE restricts one raster column per business table.

A raster dataset is made up of five tables: the business, auxiliary, block, band, and raster attribute tables. The following are the business and raster tables for a raster dataset called WORLD_TIF.

WORLD raster dataset tables in DB2

There can also be additional attribute tables as part of the raster dataset or raster catalog. There would only ever be one raster attribute table per raster dataset, but raster catalogs could have several such tables. The raster attribute tables are used to define attributes for particular raster cell values. See Raster dataset attribute tables for information on using these tables.

You can use the Build Raster Attribute tool of the Raster Properties toolset in the Raster toolset of the Data Management toolbox. See the topic Build Raster Attribute Table (Data Management) for details on this tool.

For raster datasets, the table name is in the format SDE_VAT_<raster_column_ID>. For raster catalogs, the table name is in the format SDE_VAT_<raster_column_ID>_<Object_ID>.

Raster catalogs and datasets are tracked in the system table GDB_RASTERCATALOGS. Like other types of data, raster catalogs and datasets are also tracked in the GDB_OBJECTCLASSES and LAYERS tables. Columns of type raster are tracked in the RASTER_COLUMNS table—there is one entry for every table containing a raster column. Click on the link below to view the raster dataset tables and system tables of the WORLD_TIF raster dataset. Dashed lines indicate implicit relationships between columns, solid lines mean the relationships are explicitly defined, and gray tables are views. You will need Adobe Acrobat Reader to open the diagram.

DB2 raster dataset diagram

The owner fields in the GDB_OBJECTCLASSES, TABLE_REGISTRY, COLUMN_REGISTRY, RASTER_COLUMNS, and LAYERS tables all contain the same value, but to keep the diagram from being too cluttered, the implicit relationship between these fields is not shown. The same is true for the database name field in these tables; the values are the same but the relationship is not drawn on the diagram.

Rasters in an XML document

The following is a small portion of the content of an XML document for the World raster dataset. The first section is the header; subsequent lines define the dataset.

<esri:Workspace xmlns:esri="http://www.esri.com/schemas/ArcGIS/9.2" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <WorkspaceDefinition xsi:type="esri:WorkspaceDefinition">
   <WorkspaceType>esriRemoteDatabaseWorkspace</WorkspaceType> 
   <Version>sde.DEFAULT</Version> 
   <Domains xsi:type="esri:ArrayOfDomain" /> 
   <DatasetDefinitions xsi:type="esri:ArrayOfDataElement">
     <DataElement xsi:type="esri:DERasterDataset">
       <CatalogPath>/V=sde.DEFAULT/RD=sde.RJP.world_TIF</CatalogPath> 
       <Name>sde.RJP.world_TIF</Name> 
       <Children xsi:type="esri:ArrayOfDataElement">
          <DataElement xsi:type="esri:DERasterBand">
            <CatalogPath>/V=sde.DEFAULT/RD=sde.RJP.world_TIF/RB=Band_1</CatalogPath> 
            <Name>Band_1</Name> 
            <DatasetType>esriDTRasterBand</DatasetType> 
            <DSID>-1</DSID> 
            <Versioned>false</Versioned> 
            <CanVersion>false</CanVersion> 
            <HasOID>true</HasOID> 
            <OIDFieldName>ObjectID</OIDFieldName> 
            <Fields xsi:type="esri:Fields">
              <FieldArray xsi:type="esri:ArrayOfField">
                <Field xsi:type="esri:Field">
                    <Name>ObjectID</Name> 
                    <Type>esriFieldTypeOID</Type> 
                    <IsNullable>false</IsNullable> 
                    <Length>4</Length> 
                    <Precision>0</Precision> 
                    <Scale>0</Scale> 
                    <Required>true</Required> 
                    <Editable>false</Editable> 
                </Field>
                <Field xsi:type="esri:Field">
                    <Name>Value</Name> 
                    <Type>esriFieldTypeInteger</Type> 
                    <IsNullable>true</IsNullable> 
                    <Length>0</Length> 
                    <Precision>0</Precision> 
                    <Scale>0</Scale> 
               </Field>
               <Field xsi:type="esri:Field">
                    <Name>Count</Name> 
                    <Type>esriFieldTypeInteger</Type> 
                    <IsNullable>true</IsNullable> 
                    <Length>0</Length> 
                    <Precision>0</Precision> 
                    <Scale>0</Scale> 
               </Field>
             </FieldArray>
         </Fields>
         <Indexes xsi:type="esri:Indexes">
           <IndexArray xsi:type="esri:ArrayOfIndex" /> 
         </Indexes>
         <IsInteger>true</IsInteger> 
         <MeanCellHeight>0.175996089009095</MeanCellHeight> 
         <MeanCellWidth>0.176000337991447</MeanCellWidth> 
         <Height>1024</Height> 
         <Width>2048</Width> 
         <PixelType>U8</PixelType> 
         <PrimaryField>1</PrimaryField> 
         <TableType>esriRasterTableValue</TableType> 
         <Extent xsi:type="esri:EnvelopeN">
            <XMin>-179.906382261841</XMin> 
            <YMin>-90.1303147686327</YMin> 
            <XMax>180.542309944643</XMax> 
            <YMax>90.089680376681</YMax> 
            <SpatialReference xsi:type="esri:GeographicCoordinateSystem">
   <WKT>GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]]</WKT> 
          <XOrigin>-400</XOrigin> 
          <YOrigin>-400</YOrigin> 
          <XYScale>11258999068426.2</XYScale> 
          <ZOrigin>0</ZOrigin> 
          <ZScale>1</ZScale> 
          <MOrigin>0</MOrigin> 
          <MScale>1</MScale> 
          <XYTolerance>8.98315284119521E-09</XYTolerance> 
          <ZTolerance>2</ZTolerance> 
          <MTolerance>2</MTolerance> 
          <HighPrecision>true</HighPrecision> 
          <LeftLongitude>-180</LeftLongitude> 
         </SpatialReference>
        </Extent>
      </Data>
    </DatasetData>
   </WorkspaceData>
</esri:Workspace>