OpenEdge Data Management: DataServer for Microsoft SQL Server

Appendix C: Data Type Details
7. When you define a binary or char column to allow nulls, MSS stores the data type definitions as
varbinary and varchar respectively. This does not affect how the DataServer maps the MSS data
types to OpenEdge data types.
8. When migrating an OpenEdge database to SQL Server, character fields whose format is less than x(8000)
are defined as VARCHAR by default if “ABL format” is used for field widths during migration. Fields whose
SQL widths are less than 8000 are defined as varchar by default if “width” is used for fields widths during
migration, and larger character fields are defined as VARCHAR(MAX). When the database uses unicode
data types, the 800 byte record limit in SQL Server must be expressed in 4000 characters, so the above
limits are halved for unicode data.
If there are several large character fields in one record that each individually fall under the maximum size
limits so as to be defined as varchar, but in sum, exceed the maximum record size for SQL server, it will
be necessary to define the fields as a server CLOB type, such as varchar(max) in order to successfully
create the records.
The default server type mapping for character data that exceeds the SQL Server record size limit is
changed from Text/ntext to varchar(max)/nvarchar(max) in SQL Server 2005 and later.
9. The amount of data that can be accessed in a field defined to be CHARACTER by an OpenEdge application
is limited by the maximum size of a record that can be passed to the client. The maximum record size for
DataServer applications is 30,000 bytes. Keep this in mind if you decide to map server CLOB type to
CHARACTER rather than CLOB. If you map server LOB data to CHARACTER data types but you don’t
process the data in these fields on the returned records, it is recommended that you construct field lists
to exclude them from your query results.
10. By default, the initial value of a MS SQL Server datetime or smalldatetime column is the Unknown value
(?). The default initial values for binary and varbinary are also the Unknown value (?). The MS SQL
Server datetime and smalldatetime data types contain both date and time information. The DataServer
maps these to the OpenEdge DATE data type; however, you can change the DATE data type to
CHARACTER in the schema holder. If you do this, remember to change the format to match the new data
type. For example, if you change the data type to CHARACTER, specify a character format, such as x(26).
11. When mapping of the MS SQL Server datetime or smalldatetime data types is to the OpenEdge DATE
data type, OpenEdge truncates the time portion of the date.
12. The DataServer considers this data type to be a hidden value. Its value is set by the server rather than
the application. However, you can still access a MS SQL Server table that contains this type of column.
13. Identity columns are limited by SQL Server to one per table. The PROGRESS_RECID identity column
can be auto-generated in a migrated table in order to represent ROWID for OpenEdge for that table. Your
SQL Server table can define an alternative identity column but a user-defined identity column cannot be
used like PROGRESS_RECID to represent ROWID. See the “ROWID function” section on page 121 for
more information.
356 OpenEdge Data Management: DataServer for Microsoft SQL Server