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FAQ: What is the purpose of the SE_ANNO_CAD_DATA column?

Question

What is the purpose of the SE_ANNO_CAD_DATA column?

Answer

ArcSDE supports shapes that include CAD information and SDE 3-style annotation. CAD information is used to store curves, and is required to enable interoperability for ArcCAD and CAD Client. SDE 3-style annotation is a simple annotation storage scheme used in SDE 3 client applications (not ArcGIS.) When data is stored in ArcSDE compressed binary format, the geographic elements supporting CAD and annotation are stored in the binary column of the feature table. Any annotation text is stored in the ANNO_TEXT column in the feature table.

The SDO_GEOMETRY data type is used for geometry storage in Oracle Spatial. It does not directly support annotation features, parametric curve features or CAD data. Therefore, when creating new feature classes using SDO_GEOMETRY, ArcSDE implements these types of features through a BLOB column called SE_ANNO_CAD_DATA. This column is created in the base table along with the SDO_GEOMETRY column. Whenever a feature class is created using ArcGIS, ArcSDE assumes that this column will be needed. If annotation will be stored in the feature class, a VCHAR2 column, SE_ANNO_TEXT, is also added to the base table to store the text of the annotation.

A BLOB column type was chosen for SE_ANNO_CAD_DATA in order to support replication in Oracle in the future.

The column is created by ArcSDE when it is deemed possible that the column will be needed. If the feature class is created by ArcSDE and ArcSDE creates the SE_ANNO_CAD_DATA column, that column should be left alone. Users should not drop it. An empty SE_ANNO_CAD_DATA column only occupies a few bytes per row, so the space gained by dropping the row would be minimal. If the column were missing, two problems would result. The most important is that the queries on this table will fail because the queries expect the column to exist. Secondly, if the column is needed for holding CAD data for a new row, the insert will fail if they contain data that ArcSDE would normally place in this column.