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Intructions provided describe how to estimate raster storage requirements for ArcSDE on Oracle. Prior to importing large amounts of raster data into ArcSDE, it can be important to know in advance how much storage space is required. Storage requirements for ArcSDE rasters are influenced by several factors, including the color depth; number of bands; and loading parameters, such as tile size, compression, and reduced-resolution pyramids. Guidelines are provided for estimating raster storage requirements for ArcSDE on Oracle.
ArcSDE provides two methods for compressing image data to save space and improve performance: LZ77 and JPEG. The degree of compression depends on the distribution of pixel values in the image. Images with larger areas of similar colored pixels generally compress better than more heterogeneous images. To estimate storage requirements for ArcSDE rasters, it is necessary to load one or more sample images that are representative of the entire set in terms of size and heterogeneity and examine their storage usage in Oracle.
SQL>SELECT rastercolumn_id from sde.raster_columns where table_name = ";"
SQL>SELECT SUM(bytes) / 1048576 size_in_megs FROM user_segments WHERE segment_name = 'SDE_BLK_<raster column id>';