Btrieve (transactional) Interface Components

The set of Btrieve components includes the following:

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TPvSession

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•

•

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These components use no relational functionality, and do not require the Pervasive PSQL relational interface or ODBC at runtime.

The components replace Embarcadero ones as listed in the following table.


Pervasive Direct Access Component	Replaces This Embarcadero Component
TPvBatchMove	TBatchMove
TPvDatabase	TDatabase
TPvSession	TSession
TPvTable, TwwPvTable	TTable

The components can be used standalone (that is, without the Borland Database Engine (BDE) installed) or coincident with the BDE within a single application. Use of the components is the same as the corresponding BDE components, with exceptions noted under specific components where applicable and in PDAC Classes, Properties, Events, and Methods.

TPvSession

Provides thread safety and Client ID support. Its functionality is similar to the TSession VCL component.

Related Information

See the following in this chapter pertaining to TPvSession:

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Class TPvSessionList/TPvSqlSessionList (under Supporting Classes)

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Global Variables (under General Differences from VCL)

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TPvSession and TPvSqlSession (under Specific Class Differences from VCL)

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TPvSession Specific (under Specific Class Differences from VCL)

TPvDatabase

Provides database connection-specific functionality for non-SQL databases, such as login control, transaction support, persistent database connections. Its functionality is similar to the TDatabase VCL component.

Functional Differences Between TPvDatabase and Embarcadero Components

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Property DriverName, Locale, and TTraceFlags have been dropped

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Handle's type is changed to DRM_DBID

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IsSQLBased always returns False

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TransIsolation has only two possible values: tiDirtyRead and tiReadCommitted (the default).

Secure Tables and Prompting for User Name and Password

If you are connecting to a secure table, PDAC prompts you for the user name and password. If you want suppress these prompts, set up connection parameters in TPvDatabase using the following as an example. (See also Table Security under TPvTable.)

PvSession.ServerName:='ServerName';

PvSession.SessionName:='session1';

PvSession.Active:=True;

PvDatabase.AliasName:= 'DatabaseName';

PvDatabase.DatabaseName:='DB';

PvDatabase.SessionName:='session1';

PvDatabase.Params.Clear();

// here you specify user name and password to

// connect to remote database.

PvDatabase.Params.Add('User Name=UserName');

PvDatabase.Params.Add('password=Password');

PvDatabase.Connected:=True;

PvTable.DatabaseName:='DB';

PvTable.SessionName:='session1';

PvTable.TableName:='person';

PvTable.Active:=True;

Related Information

See the following in this chapter pertaining to TPvDatabase:

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TransIsolation Property Differences (under Differences Betweeen PDAC and Embarcadero Components

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TPvDatabase and TPvSqlDatabase (under Specific Class Differences from VCL)

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TPvDatabase Specific (under Specific Class Differences from VCL)

TPvTable

Provides single-table access and manipulation. Its functionality is similar to the TTable VCL component.

Functional Differences Between TPvTable and Embarcadero Components

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All alias management functions perform ”named database” management.

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Inherits from TPvDataSet rather than TDBDataSet;

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Properties TableLevel, UpdateObject, UnlockTable, OpenIndexFile, CloseIndexFile have been dropped, TableType is ignored.

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The Database Name property can be provided at both design time and runtime as a DSN, a Pervasive Named Database, or as a fully-qualified path to the database.

Table Security

PDAC security for the Btrieve interface uses owner names for individual tables. Using this security model, you provide the owner name for the table. See Btrieve operation 29, Set Owner (29), in the Btrieve API Guide for more information.

The TPvTable has the property Owner: string and the following method:

SetOwnerOnTable(AOwner: string; AccessMode: integer).

With the Owner property you can set the owner name, and with the SetOwnerOnTable method you can set or clear the owner name on the table.

Table 3

PDAC Access Modes

Code

Description

Requires an owner name for any access mode (no data encryption)

Permits read-only access without an owner name (no data encryption)

Requires an owner name for any access mode (with data encryption)

Permits read-only access without an owner name (with data encryption)

To access the Btrieve table, provide a valid owner name.

Table Creation

Call the CreateTable method at runtime to create a table using this dataset’s current definition.

If the FieldDefs property contains values, these values are used to create field definitions. Otherwise the Fields property is used. One or both of these properties must contain values in order to recreate a dataset.

Use the Add method to assign field properties

procedure Add(const Name: string; DataType: TFieldType; Size: Word; Required: Boolean);

Add is provided for backward compatibility. The recommended way to add new field definitions to the Items property array is using the AddFieldDef method. You should also use it to specify precision and scale for the ftBCD data type.

Add uses the values passed in the Name, DataType, Size, and Required parameters and assigns them to the respective properties of the new field definition object.

Note Set Required to False if the field is nullable.

To activate the autoincrement property for AutoInc field, you have to create a unique index on this field.

Delphi Example

PvTable1.DatabaseName := 'TestData';

PvTable1.TableName := 'TestData1';

with PvTable1.FieldDefs do

begin

Clear;

Add('F_autoinc', ftAutoInc, 0, True);

Add('F_currency', ftCurrency, 0, False);

Add('F_integer', ftInteger, 0, False);

Add('F_word', ftWord, 0, False);

Add('F_fixchar', ftFixedchar, 30, False);

Add('F_varbin', ftString, 25, False);

Add('F_blob', ftBlob, 60, False);

end;

with PvTable1.FieldDefs.AddFieldDef do

Precision := 10; //Precision

Required := false;

end;

with PvTable1.IndexDefs do

begin

Clear;

Add('Index1', 'F_autoinc', [ixPrimary, ixUnique]);

Add('Index2', 'F_integer', [ixCaseInsensitive]);

end;

PvTable1.CreateTable;

C++ Builder Example

PvTable1->DatabaseName="TestData";

PvTable1->TableName="Test1";

PvTable1->FieldDefs->Clear();

PvTable1->FieldDefs->Add("F_autoinc", ftAutoInc, 0, True);

PvTable1->FieldDefs->Add("F_integer", ftInteger, 0, False);

PvTable1->FieldDefs->Add("F_Curr", ftCurrency, 0, False);

PvTable1->FieldDefs->Add("F_Word", ftWord, 0, False);

PvTable1->FieldDefs->Add("F_fixchar", ftFixedChar, 0, False);

PvTable1->FieldDefs->Add("F_String", ftString, 20, False);

PvTable1->FieldDefs->Add("F_blob", ftBlob, 60, False);

TFieldDef *FieldDef = PvTable1->FieldDefs->AddFieldDef();

FieldDef->Name="F_BCD";

FieldDef->DataType=ftBCD;

FieldDef->Size=2;

FieldDef->Precision=10;

FieldDef->Required=False;

PvTable1->IndexDefs->Clear();

PvTable1->IndexDefs-> Add("Index1","F_autoinc",TIndexOptions() <<ixPrimary << ixUnique);

PvTable1->CreateTable();

Related Information

See the following in this chapter pertaining to TPvTable:

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TransIsolation Property Differences (under Differences Betweeen PDAC and Embarcadero Components

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TPvTable, TPvQuery, and TPvStoredProc (under Specific Class Differences from VCL)

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TPvTable Specific (under Specific Class Differences from VCL)

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Pervasive PSQL and Embarcadero Data Types

TPvBatchMove

Enables applications to perform database operations on groups of records or entire tables. Its functionality is similar to the TBatchMove VCL component.

Related Information

See the following in this chapter pertaining to TPvTable:

•

TPvBatchMove (under Specific Class Differences from VCL)

TwwPvTable

Included with PDAC for InfoPower compatibility. It is directly derived from TPvTable and has an extra property, “Control Type.”