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 Using triggers to enable PROGRESS_RECID support of the ROWID function.
• 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.

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 Old format RECID Buffer size: the ZPRGRS_RECID_BUF_SIZE,nnn Option for more information on setting this option.