OpenEdge Data Management: DataServer for Microsoft SQL Server

Defining the ROWID
Modifying a schema holder
When you create or update a schema holder, the DataServer uses the following guidelines to
select a column in a data source table to support the ROWID function:
• If the data source table has a PROGRESS_RECID column, the DataServer selects that column.
A column of this type provides optimal support for the ROWID function; you cannot select
an alternative to it. To create a PROGRESS_RECID column, see the “Using triggers to enable
PROGRESS_RECID support of the ROWID function” section on page 7–37.
• If the data source table does not have a PROGRESS_RECID column, the DataServer evaluates
the available indexes and selects one according to the following criteria:
– The index must be defined as unique.
– The index must be defined as mandatory, or at least treated as such by your
application.
The index selection process proceeds, according to the following order:
1. If you select an index, then you must select a qualified index.
2. If you do not select an index, the MS SQL Server DataServer selects a qualified index
based on a single-component integer.
However, if the DataServer determines that more than one qualified index meets the
additional criterion as a single-component integer, the DataServer selects the first index
that fulfills the complete criteria.
3. If the MS SQL Server DataServer cannot find a qualified index based on a
single-component integer, it seeks a qualified index that is multi-component and/or
non-integer.
However, if the DataServer determines that more than one qualified index meets the
additional criterion as multi-component and/or non-integer, the DataServer selects the first
index that fulfills the complete criteria.
4. If the MS SQL Server DataServer cannot find a qualified index that is a multi-component
and/or non-integer, the task cannot be completed and ROWID support is not provided. The
table will not be able to uniquely identify any records. As a result, implementing FIND
statements and performing queries could lead to inaccuracies in locating records.
Note that the indexes in this class are not mandatory; therefore, it is essential that you enforce
the column supporting ROWID as mandatory at least through code if not through definitions.
The DataServer allocates a buffer to hold the key information for the selected RECID index. The
buffer is 245 bytes by default. If the index you select for the RECID is a multi-component index,
this may be inadequate. The size of the buffer can be modified with the -Dsrv
ZPRGRS_RECID_BUF_SIZE,n option. See the “RECID Buffer size—the
ZPRGRS_RECID_BUF_SIZE,nnn Option” section on page 8–10 for more information on
setting this option.
Note: An index that you select as a ROWID must be defined as a unique index. It must also be
mandatory, if not by definition, then by means of the application code.
7–35