The HS_DB_DOMAIN initialization parameter is similar to the DB_DOMAIN initialization parameter, described in the Oracle Database Reference. The HS_DB_DOMAIN initialization parameter is required if you use the Oracle Names server. The HS_DB_NAME and HS_DB_DOMAIN initialization parameters define the global name of the non-Oracle system.

This parameter's value is used as part of a transaction ID when global name services are activated. Specifying a nonunique number can cause problems when two-phase commit recovery actions are necessary for a transaction.

This name identifies the non-Oracle system within the cooperative server environment. The HS_DB_NAME and HS_DB_DOMAIN initialization parameters define the global name of the non-Oracle system.

This limit is known as the describe cache high water mark. The cache contains descriptions of the mapped tables that Heterogeneous Services reuses so that it does not have to re-access the non-Oracle data store.

If you are accessing many mapped tables, increase the high water mark to improve performance. Increasing the high water mark improves performance at the cost of memory usage.

The value must use the following format:

language[_territory.character_set]

A smaller piece size means less memory requirement, but more round-trips to fetch all the data. A larger piece size means fewer round-trips, but more of a memory requirement to store the intermediate pieces internally. Thus, the initialization parameter can be used to tune a system for the best performance, with the best trade-off between round-trips and memory requirements, and network latency or response time.

The value never exceeds the number of open cursors in the Oracle database. Therefore, setting the same value as the OPEN_CURSORS initialization parameter in the Oracle database is recommended.

The following values are possible:

• OFF disables reblocking of fetched data so that data is immediately sent from agent to server.

• ON enables reblocking, which means that data fetched from the non-Oracle system is buffered in the agent and is not sent to the Oracle database until the amount of fetched data is equal or higher than the value of HS_RPC_FETCH_SIZE initialization parameter. However, any buffered data is returned immediately when a fetch indicates that no more data exists or when the non-Oracle system reports an error.

Increasing the value can reduce the number of network round-trips needed to transfer a given amount of data, but also tends to increase data bandwidth and to reduce latency as measured between issuing a query and completion of all fetches for the query. Nevertheless, increasing the fetch size can increase latency for the initial fetch results of a query, because the first fetch results are not transmitted until additional data is available.

The format mask, [+|-]hh:mm, is specified to indicate the hours and minutes before or after UTC (Coordinated Universal Time—formerly Greenwich Mean Time). For example:

HS_TIME_ZONE = [+ | -] hh:mm

The following values are possible:

• READ_ONLY provides read access to the non-Oracle database.

• SINGLE_SITE provides read and write access to the non-Oracle database. However, the gateway cannot participate in distributed updates and cannot be used with Oracle Streams to replicate data.

The value should be an absolute path and should not contain environment variables. The three levels of nesting limit do not apply.

If set to CHAR , then non-Oracle target timestamp would be mapped to CHAR(26). If set to DATE (default), then non-Oracle target timestamp would be mapped to Oracle DATE. If set to TIMESTAMP, then non-Oracle target timestamp would be mapped to Oracle TIMESTAMP.

If set to CHAR, then non-Oracle target date would be mapped to CHAR(10). If set to DATE, then non-Oracle target date would be mapped to Oracle Date.

The default initialization parameter file already has an entry for this parameter. The syntax for HS_FDS_CONNECT_INFO for the gateway is as follows:

HS_FDS_CONNECT_INFO=dsn_value

where, dsn_value on Microsoft Windows, is the name of the system DSN defined in the Microsoft Windows ODBC Data Source Administrator and on UNIX based system, it is data source name configured in the odbc.ini file.

The entry for dsn_value is case sensitive.

The following values are valid:

• OFF disables the tracing of error messages.

• ON enables the tracing of error messages that occur when you encounter problems. The results are written by default to a gateway log file in LOG directory where the gateway is installed.

• DEBUG enables the tracing of detailed error messages that can be used for debugging.

This is a required parameter, whose format is:

HS_FDS_SHAREABLE_NAME=odbc_installation_path/lib/libodbc.sl

Where:

odbc_installation_path is the path where the ODBC driver is installed.

This parameter applies only to UNIX based platforms.

This parameter will be affected by the HS_RPC_FETCH_SIZE and HS_RPC_FETCH_REBLOCKING parameters.

As more Oracle databases and non-Oracle databases use Unicode as database character sets, it is preferable to also run the gateway in Unicode character set. To do so, you must set HS_LANGUAGE=AL32UTF8. However, when the gateway runs on Windows, the Microsoft ODBC Driver Manager interface can exchange data only in the double-byte character set, UCS2. This results in extra ratio expansion of described buffer and column sizes. To compensate, the gateway can adjust to correct size if HS_FDS_REMOTE_DB_CHARSET is set to the corresponding non-Oracle database character set. For example, HS_FDS_REMOTE_DB_CHARSET=KO16KSC5601.

In order for Oracle Database Gateway for ODBC to compensate their behavior, you need to specify HS_FDS_SQLLEN_INTERPRETATION=32 if you use these types of driver managers and driver.

The default value is FALSE.