Overview | Environments | Datatypes | Exporting | Limitations | Example

Fixed-length files are often the highest performing and most flexible approach to indexing large amounts of data, but they do have some limitations. These limitations are described below:

• Datatypes - Fixed-length files can store nearly every datatype supported by Omnidex, including proprietary datatypes such as ORACLE DATETIME or ODBC DATETIME. An exception to this is the relational datatypes, VARCHAR and CLOB. These datatypes cannot be represented in fixed-length files because they require separate storage for length and NULL indicators. For fixed-length files, the STRING and CHARACTER datatypes should be used instead.

• NULL's - Fixed-length files are not capable of differentiating a NULL column as is done in relational databases. Omnidex will treat empty fields as NULL fields to compensate for this. For character-class datatypes, an IS NULL test will qualify any row containing an empty space in that column. For binary-class datatypes, an IS NULL test will qualify any row containing a zero in that column.

• Deletes - Omnidex supports INSERT and UPDATE statements against fixed-length files, but it cannot support the DELETE statement. If DELETE statements are required, consider using Omnidex Standalone Tables.

• Compression - Fixed-length files require the same number of bytes per row, regardless of the content of the data. This can lead to excessive use of disk space if tables have large textual columns. For example, an email address column may be sized at 320 bytes, consistent with the published standard; however, most people have relatively short email addresses. If the average email address is 20 characters long, then most rows will waste nearly 300 bytes. This will waste disk space and degrade performance. In these situations, delimited files or Omnidex Standalone Tables will provide a better solution.

• Security - Fixed-length data files are not encrypted as they might be in a relational database. Care should be taken with file system security to properly protect the data.

Despite these limitations, fixed-length files usually provide the most flexible, portable, and high-performing solution possible, and are a favorite solution with Omnidex.

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