3 2 4 Data Access

LANSA Open Guide

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3.2.4 Data Access

The majority of your applications will consist of data related functions.

Once your application has opened a communications session, it can access the data on the host. Using LANSA Open, you can get, add, change and delete information on the host. You may also execute LANSA and other host programs.

There are a wide range of data access functions. These functions have been grouped into the following functional areas:

File Processing - Single Record	These functions are used to fetch, add, change or delete a single record from the host.
File Processing - Multiple Record	These functions are used to retrieve one or more records from the host.
File Commitment Control	These functions are used if you have commitment control invoked for your host database.
Retrieving Repository Details	These functions are used to retrieve information, such as descriptions, labels and column headings, which are stored in the host Repository.
Manipulating Field Data	These functions are used to use or prepare the current value for a field.
Calling Processes on the Host	These functions are used to execute LANSA and iSeries programs or OS/400 functions.
Message/Error Handling	LANSA Open has its own automated error management facility, or alternatively, your application can perform its own error handling using the functions provided.

File Processing - Single Record

The LceInsert, LceUpdate and LceDelete functions have a validate parameter which allows a check to be made without performing the actual operation.

LceCheckFor	Checks for the existence of a record in the specified file. The validate parameter of the insert, update or delete function can be used instead of this function.
LceSetSelectOptions	Specifies the select or fetch options.
LceFetch	Fetches the values of the specified fields from the specified file.
LceInsert	Inserts the values of the specified fields into a record.
LceUpdate	Updates the record with the values in the fields specified.
LceDelete	Deletes a record from the specified file.

Note: When multiple users are accessing a database, eventually two or more users will want to update the same record at the same time.

What should you do about this?

Refer to the LceUpdate or LceDelete function details to find out.

File Processing - Multiple Record

LceRequestSelect	Selects records on the host.
LceRequestSelectWhere	Provides a 'where' condition to be used when selecting records on the host.
LceReceiveSelect	Transfers records from the host to the PC.
LceGetRecordCount	Determines how many records were transferred from the host.
LceGetSelect	Retrieves the next record from the records transferred to the PC.
LceSelect	Selects and retrieves specified fields from file.
LceReceiveNextX	Gets the next record transferred from the host.
LceDeleteSelect	Deletes the temporary file used to hold the host records transferred to the PC.

File Commitment Control

These functions are only effective if the LceSetCommitmentOn function has been executed and Commitment Control definitions have been configured correctly on the host files.

LceCommitWork	Commits the current transaction.
LceRollBackWork	Rolls back the current transaction.

Retrieving Repository Details

These functions are used to retrieve information from the Repository for your PC application:

LceGetFieldDesc	Retrieves the field description.
LceGetFieldHeading	Obtains the three line field heading.
LceGetFieldIndicator	Returns the DBCS field indicator.
LceGetFieldLabel	Returns the field label.
LceGetFieldType	Returns the field type.
LceGetFieldValueH	Sets the window text field value.
LceGetFileDesc	Returns the file description.
LceGetFileType	Returns the file type.
LceGetVariable	Retrieves the system or multilingual variable.
LceGetFieldEdit	Fetches the edit code or word.
LceGetDefaultValueX	Returns the field's default value.
LceGetFieldHelpText	Returns the field's help text to a buffer or displays it in a window.
LceGetFieldAttributes	Returns the field's attributes.

Manipulating Field Data

LceGetFieldValueX	Retrieves the field's current value.
LceSetFieldValue	Sets the field value in the field information area.
LceLocalDateTimeToServer	Converts the DateTime from the client's local timezone into UTC (Universal Coordinated Time). This function is for use in creating Where clauses which contain DateTime values.
LceGetFieldDataLength	Retrieve the length of the field's current value.

Calling Processes on the Host

These functions allow you to execute processes on the host.

By re-using existing host processes and functions, significant savings can be made in development time. Consistency between client and host processes is also maintained.

For tasks requiring access to multiple files, perform them on the host, to allow your client applications to benefit from the host's fast file processing.

LceLansaCall	Executes a LANSA process/function or an iSeries program with an immediate response.
LceExecute400	Executes the specified function on the iSeries.
LceSubmit	Submits a LANSA process/function or an iSeries program in batch mode.
Lce3GLDefineParameter	Defines the attributes and optionally sets the values of the parameter used in the Lce3GLCall function.
Lce3GLCall	Executes the specified 3GL program on the iSeries.
Lce3GLGetValue	Fetches the parameter value returned by the Lce3GLCall function.

Message/Error Handling

There are two ways to manage your error messages.

You can:

let LANSA Open perform all the error message handling automatically

do your own error message handling.

LceDisplayErrors	Displays error messages automatically.
LceGetStatus	Returns the error status and message, if any.
LceGetMessageCount	Counts the number of messages sent by the Host System.
LceGetMessage	Returns the specified error message.

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