PSQL Engine DSN Setup

PSQL Engine DSN Setup

Note that Engine DSNs are 32-bit only.

Windows 64-bit operating systems contain two different executable files for ODBC Administrator, one for 32-bit DSNs and one for 64-bit DSNs. Each ODBC Administrator lists only the system DSNs that match its bitness. That is, the 64-bit ODBC Administrator lists 64-bit system DSNs, and vice versa. If you start ODBC Administrator from the Windows Control Panel, the 64-bit version is run. The 64-bit version does not list Engine DSNs because they are 32-bit only.

PSQL Control Center (PCC) contains separate options in the Tools menu to start the 32-bit or the 64-bit ODBC Administrator. Note that, if an ODBC Administrator is already open, Windows defaults to it. That is, if the 32-bit ODBC Administrator is open and you attempt to start the 64-bit one, Windows displays the 32-bit version (and vice versa). In other words, only one version of the ODBC Administrator runs at a time. This is a limitation of the Windows operating system, not PSQL.

Note: New or revised 32-bit applications, local or remote, should connect to a named database, not to an Engine DSN. Alternately, applications could use DSN-less connections (see DSN-less Connections). Avoiding the use of Engine DSNs positions your application for the future when Engine DSNs will no longer be supported in PSQL.

Data Source Name

The ODBC client-server architecture calls for the naming of each specific data set so that it can be referred to by a well-known name.

Type a name (called a data source name, or DSN) for the data source to which you wish to set up a connection. This DSN will help you identify the data source.

For additional information about using DSNs with the database engine, see ODBC Database Access.

Type a description of the DSN, if desired, to help identify the DSN, database, or application.

Select a database with which you want to associate the DSN. Optionally, you may create a new database by clicking Create.

Database Configuration Details

See Create Database Through DSN Setup for the following database configuration details:

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Dictionary Location

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Data File Location

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Integrity Enforced

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Engine DSN Advanced Connection Attributes

The connection attributes for Engine DSNs include the following:

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Encoding Translation

Note: Engine DSNs are deprecated. New or updated applications should use Client DSNs in local or remote connection mode.

The DSN Open Mode options for Engine DSNs allow you to specify one of several characteristics that go into effect when tables are opened through the specified DSN. These options are mutually exclusive—you are not permitted to select more than one.

These options correspond directly to the Btrieve open modes allowed in the Open (0) operation. By setting an Open Mode for a DSN, you are setting the default behavior for tables (corresponding to Btrieve files) opened through that DSN.

Table 13

DSN Open Modes and ODBC Connection Options

ODBC Connection String Generated

SQLSetConnectOption Call

SQLSetConnectOption( pSubDbc, SQL_ACCESS_MODE, SQL_MODE_READ_WRITE);

SQLSetConnectOption is ignored

SQLSetConnectOption( pSubDbc, SQL_ACCESS_MODE, SQL_MODE_READ_ONLY);

SQLSetConnectOption is ignored

Normal mode is the default. Opening a table in Normal mode allows read/write access according to the permissions defined in the database.

If this mode is selected, the ODBC connection string includes OPENMODE=0, and the following ODBC function call is executed when you connect to the database:

SQLSetConnectOption(pSubDbc, SQL_ACCESS_MODE, SQL_MODE_READ_WRITE);

Opening a table in Accelerated mode provides increased insert/update performance by disabling database engine logging functions for the current user. The changes to logging in Accelerated mode do not affect other users accessing the same table.

Caution: The database engine cannot guarantee transaction atomicity, transaction durability, or archival log safety for any client during use of Accelerated mode by any client. The reason for this restriction is that in the event a restore from log is needed, the log may not contain adequate information to complete the restore, because it is only a partial record of operations on a data file.

For example, if a system failure occurs while the same file is being accessed by a client performing inserts using Accelerated mode and a client performing updates using Normal mode, it is possible for the transaction log to contain updates to records that do not yet exist in the data files, because the Accelerated insert operation in memory was never flushed to disk, while the transactional update operation was written to the transaction log.

An attempt to roll forward an archival log containing this combination of operations will fail.

When this mode is selected, the ODBC connection string includes OPENMODE=-1, and the SQLSetConnectOption call is ignored by the ODBC driver. You cannot use SQLSetConnectOption to specify this mode.

When a table is opened in read-only mode, operations that modify the database structure or the data in the database are not permitted.

If this mode is selected, the ODBC connection string includes OPENMODE=1, and the following ODBC function call is executed when you connect to the database:

SQLSetConnectOption(pSubDbc, SQL_ACCESS_MODE, SQL_MODE_READ_ONLY);

When a table is opened in exclusive mode, no other connections to the table are permitted. If other users are currently accessing the given table, it cannot be opened in Exclusive mode. You must try again later.

When this mode is selected, the ODBC connection string includes OPENMODE=-4, and the SQLSetConnectOption call is ignored by the ODBC driver. You cannot use SQLSetConnectOption to specify this mode.

Encoding Translation

The encoding translation options are the same as for Client and 64-bit DSNs. See Encoding Translation.