HTransactionStart (Function)

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Network application (ISAM database)
Locking records
Error cases
Temporary files created during the transaction (ISAM database)
Handling records during a transaction
Transactions and independent HFSQL context
OLE DB and Native Connectors

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HTransactionStart (Function)

In french: HTransactionDébut

Not available with this kind of connection

Starts a transaction on the data files (HFSQL or accessed via a Native Connector) and creates the transaction file.

What information is saved in the transaction file? Whenever a WLanguage function modifies a data file or an index file during a transaction, the former values of the record and the operation performed are stored in the transaction file.

This function proposes two operating modes of transactions:

Versions 19 and later
The transaction can be started on a connection: In this case, a transaction is started only for files associated to this connection. This mode is required to manage the isolation levels of transactions.
New in version 19
The transaction can be started on a connection: In this case, a transaction is started only for files associated to this connection. This mode is required to manage the isolation levels of transactions.
The transaction can be started on a connection: In this case, a transaction is started only for files associated to this connection. This mode is required to manage the isolation levels of transactions.
The transaction can be started on all HFSQL connections (existing ones or future ones). In this case, HTransactionStart starts both an HFSQL Classic transaction (ISAM) and an HFSQL Client/Server transaction.

Versions 17 and later

This function is now available for iPhone/iPad applications.

New in version 17

This function is now available for iPhone/iPad applications.

The management of transactions is available for the HFSQL Client/Server databases.

Versions 18 and later

This function is now available in Windows Store apps mode.

This function is now available in Android Widget mode.

This function is now available for the Java applications.

This function is now available for Android applications.

New in version 18

This function is now available in Windows Store apps mode.

This function is now available in Android Widget mode.

This function is now available for the Java applications.

This function is now available for Android applications.

This function is now available in Windows Store apps mode.

This function is now available in Android Widget mode.

This function is now available for the Java applications.

This function is now available for Android applications.

Remark: From version 19, HFSQL is the new name of HyperFileSQL.

Versions 21 and later

This function is now available in Universal Windows 10 App mode.

New in version 21

This function is now available in Universal Windows 10 App mode.

Versions 23 and later
Remark: This function is equivalent to HTransaction.

New in version 23
Remark: This function is equivalent to HTransaction.

Remark: This function is equivalent to HTransaction.

Example

Versions 19 and later

MyConnection1 is Connection

// Start transaction on data files associated with MyConnection1
HTransactionStart(MyConnection1)

// Code used to prepare the order to added
// ...

WHEN EXCEPTION IN
// Add the order
HAdd(Orders)
// Validate the addition
HTransactionEnd(MyConnection1)
DO
// Delete the order lines
HTransactionCancel(MyConnection1)
END

New in version 19

// Start transaction on the Orders and OrdLine data files
HTransactionStart("C:\Temp\Transaction.trs", "Orders,OrdLine,-Customer")

// Code used to prepare the order to added
// ...

WHEN EXCEPTION IN
// Add the order
HAdd(Orders)
// Validate the addition
HTransactionEnd()
DO
// Delete the order lines
HTransactionCancel()
END

Syntax

Versions 19 and later

Starting a Client/Server transaction on a specific connection Hide the details

<Result> = HTransactionStart(<Connection> [, <List of data files>])

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Connection>: Character string (with or without quotes) or Connection variable

Name of connection to use. This connection corresponds to:
the name of the connection defined in the data model editor or with HDescribeConnection or HOpenConnection.
the name of a Connection variable.
If this parameter corresponds to the hAccessHF7 constant, the transaction will be performed on HFSQL ISAM files.

<List of data files>: Optional character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
The files not specified in the list will be excluded from the transaction.
This parameter is ignored. All the data files associated with the connection are in transaction on the native server.

New in version 19

Starting a Client/Server transaction on a specific connection Hide the details

<Result> = HTransactionStart(<Connection> [, <List of data files>])

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Connection>: Character string (with or without quotes) or Connection variable

Name of connection to use. This connection corresponds to:
the name of the connection defined in the data model editor or with HDescribeConnection or HOpenConnection.
the name of a Connection variable.
If this parameter corresponds to the hAccessHF7 constant, the transaction will be performed on HFSQL ISAM files.

<List of data files>: Optional character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
The files not specified in the list will be excluded from the transaction.
This parameter is ignored. All the data files associated with the connection are in transaction on the native server.

Starting a Client/Server transaction on a specific connection Hide the details

<Result> = HTransactionStart(<Connection> [, <List of data files>])

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Connection>: Character string (with or without quotes) or Connection variable

Name of connection to use. This connection corresponds to:
the name of the connection defined in the data model editor or with HDescribeConnection or HOpenConnection.
the name of a Connection variable.
If this parameter corresponds to the hAccessHF7 constant, the transaction will be performed on HFSQL ISAM files.

<List of data files>: Optional character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
The files not specified in the list will be excluded from the transaction.
This parameter is ignored. All the data files associated with the connection are in transaction on the native server.

Versions 19 and later

Starting a Client/Server transaction on a specific connection or an ISAM transaction Hide the details

<Result> = HTransactionStart(<Connection> , <Transaction file> , <List of data files>)

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Connection>: Character string (with or without quotes) or Connection variable

Connection to use. This connection corresponds to:
the name of the connection defined in the data model editor or with HDescribeConnection or HOpenConnection.
the name of a Connection variable.
If this parameter corresponds to an empty string ("") or to the hAccessHF7 constant, the transaction is performed on HFSQL ISAM data files.

<Transaction file>: Character string (with quotes)

Full name of transaction file (used to store the operations performed in transaction). This file will be automatically deleted when using HTransactionEnd or HTransactionCancel.
If this name corresponds to an empty string, the transaction file will be created in the directory of application files and it will be named: <Project Name>_$TRS_OPERATION.TRS.
This parameter is ignored. This parameter is taken into account for the HFSQL Classic transactions only (ISAM transactions).

<List of data files>: Character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
Data files not specified in the list will be excluded from the transaction.
This parameter is ignored. All the data files associated with the connection are in transaction on the native server.

New in version 19

Starting a Client/Server transaction on a specific connection or an ISAM transaction Hide the details

<Result> = HTransactionStart(<Connection> , <Transaction file> , <List of data files>)

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Connection>: Character string (with or without quotes) or Connection variable

Connection to use. This connection corresponds to:
the name of the connection defined in the data model editor or with HDescribeConnection or HOpenConnection.
the name of a Connection variable.
If this parameter corresponds to an empty string ("") or to the hAccessHF7 constant, the transaction is performed on HFSQL ISAM data files.

<Transaction file>: Character string (with quotes)

Full name of transaction file (used to store the operations performed in transaction). This file will be automatically deleted when using HTransactionEnd or HTransactionCancel.
If this name corresponds to an empty string, the transaction file will be created in the directory of application files and it will be named: <Project Name>_$TRS_OPERATION.TRS.
This parameter is ignored. This parameter is taken into account for the HFSQL Classic transactions only (ISAM transactions).

<List of data files>: Character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
Data files not specified in the list will be excluded from the transaction.
This parameter is ignored. All the data files associated with the connection are in transaction on the native server.

Starting a Client/Server transaction on a specific connection or an ISAM transaction Hide the details

<Result> = HTransactionStart(<Connection> , <Transaction file> , <List of data files>)

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Connection>: Character string (with or without quotes) or Connection variable

Connection to use. This connection corresponds to:
the name of the connection defined in the data model editor or with HDescribeConnection or HOpenConnection.
the name of a Connection variable.
If this parameter corresponds to an empty string ("") or to the hAccessHF7 constant, the transaction is performed on HFSQL ISAM data files.

<Transaction file>: Character string (with quotes)

Full name of transaction file (used to store the operations performed in transaction). This file will be automatically deleted when using HTransactionEnd or HTransactionCancel.
If this name corresponds to an empty string, the transaction file will be created in the directory of application files and it will be named: <Project Name>_$TRS_OPERATION.TRS.
This parameter is ignored. This parameter is taken into account for the HFSQL Classic transactions only (ISAM transactions).

<List of data files>: Character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
Data files not specified in the list will be excluded from the transaction.
This parameter is ignored. All the data files associated with the connection are in transaction on the native server.

Starting an ISAM and/or Client/Server transaction on all the HFSQL Client/Server connections (existing ones or future ones) Hide the details

<Result> = HTransactionStart([<Transaction file> [, <List of files>]])

<Result>: Boolean

True if the transaction was started,
False if a problem occurred. HErrorInfo returns more details about the error.

<Transaction file>: Optional character string (with quotes)

Full name of transaction file (used to store the operations performed in transaction). This file will be automatically deleted when using HTransactionEnd or HTransactionCancel.
If this name is not specified or if it corresponds to an empty string, the transaction file will be created in the directory of the data files of the application and it will be named: <Project Name>_$TRS_OPERATION.TRS.
This parameter is ignored. This parameter is taken into account for the HFSQL Classic transactions only (ISAM transactions).

<List of files>: Optional character string (with quotes)

List of logical names of one or more data files to take into account (or not) in the transaction (in this case, the data file name is preceded by the "-" sign).
If this parameter is not specified All data files used during the transaction will be taken into account in the transaction.
If all data files are prefixed with the "-" sign
For example: "-Customer, -Product" All data files specified in the list and used during the transaction will not be taken into account by the transaction.
All data files not specified in the list will be taken into account and used during the transaction.
If no data file on the list is prefixed with the "-" sign
For example: "Customer, Product" All data files specified in the list and used during the transaction will be taken into account in the transaction.
All data files not specified and manipulated during the transaction will be ignored in the transaction.
If some data files are prefixed with "-" and others are not
For example: "-Customer, Product" (equivalent to "Product") All data files in the list prefixed with "-" and used during the transaction will be ignored in the transaction.
All data files in the list not prefixed with "-" and used during the transaction will be taken into account in the transaction.
Data files not specified in the list will be excluded from the transaction.

Remarks

Network application (ISAM database)

In network, the transaction file can be created on a local disk or on a network drive.

If the transaction file is installed on a local computer, this file will contain information regarding the transactions performed by the current computer. In this case, the transaction file is deleted when the transaction is ended.
If the transaction file is installed on a network drive (recommended), this file will contain information regarding the transactions performed by several computers. Each computer is identified by a unique number. In this case, the transaction file is deleted when the last transaction is ended.

Locking records

The added, modified or deleted records in a transaction are locked in write mode.

Error cases

Nesting transactions: Transactions cannot be nested (i.e. HTransactionStart cannot be called in a transaction). In this case, error 70031 occurs.
Versions 19 and later
A fatal error is displayed in the following cases:
- A transaction is started on all the connections while there is at least one connection in transaction.
- A transaction is started on a connection while a transaction was already started on all the connections.
- A transaction is started on all the connections while there is at least one connection whose isolation mode is not "Read Uncommitted".
New in version 19
A fatal error is displayed in the following cases:
- A transaction is started on all the connections while there is at least one connection in transaction.
- A transaction is started on a connection while a transaction was already started on all the connections.
- A transaction is started on all the connections while there is at least one connection whose isolation mode is not "Read Uncommitted".
A fatal error is displayed in the following cases:
- A transaction is started on all the connections while there is at least one connection in transaction.
- A transaction is started on a connection while a transaction was already started on all the connections.
- A transaction is started on all the connections while there is at least one connection whose isolation mode is not "Read Uncommitted".

Temporary files created during the transaction (ISAM database)

During the transaction, temporary files (".TRX" extension) are created in the directory containing the data files (".FIC" files). These temporary files must not be deleted. Otherwise, the data handled by the transaction could be damaged.

Remark: These temporary files are automatically deleted at the end of the transaction.

Handling records during a transaction

During a transaction, some rules must be complied with when handling the records. See Transactions: Handling records during a transaction for more details.

Transactions and independent HFSQL context

When copying a context, if a transaction is in progress on the first context, the new context is not in transaction. You must call HTransactionStart to start a transaction in the new context.

OLE DB and Native Connectors

HTransactionStart cannot be used in this version. To start a transaction, use SQLTransaction.Only the syntaxes with connection are taken into account by the Native Accesses that support the transactions. You can also use SQLTransaction.

Component : wd250hf.dll