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When the server accesses a data source, it needs to know how to interpret the data stored there. For each data source the server will access, you create a synonym that describes the data source structure and the server mapping of the Informix data types.
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Synonyms define unique names (or aliases) for each Informix table or view that is accessible from the server. Synonyms are useful because they hide the underlying data source location and identity from client applications. They also provide support for the extended metadata features of the server, such as virtual fields and additional security mechanisms.
Using synonyms allows an object to be moved or renamed while allowing client applications to continue functioning without modification. The only modification required is a redefinition of the synonym on the server. The result of creating a synonym is a Master File and an Access File, which represent the server metadata.
The Applications page opens.
The Connect to Data page opens.
Depending on the type of adapter you chose, one of the following options appears on the context menu.
The button may be labeled Next, Create Synonym, Create Base Synonyms, Create Cluster Synonym, or Update Base Synonyms.
The synonym creation process for most adapters has been consolidated so that you can enter all necessary parameters on one page. However, for some adapters such as LDAP, you must click Next buttons until you get to a page that has a Create Synonym button.
The synonym is created and added under the specified application directory.
Note: When creating a synonym, if you choose the Validate check box (where available), the server adjusts special characters and checks for reserved words. For more information, see Validation for Special Characters and Reserved Words.
The following list describes the synonym creation parameters for which you can supply values.
Restrict candidates for synonym creation based on the selected object type(s): Tables, Views, External SQL Scripts, and any other supported objects.
Choosing External SQL Scripts from the drop-down list enables you to represent an SQL Query as a synonym for read-only reporting. A Synonym candidate can be any file that contains one (and only one) valid SQL Query and does not contain end-of-statement delimiters (";" or "/") and comments.
Depending on the adapter, you can further restrict your search by choosing check boxes for listed objects.
To specify a database from which you can select a table or other object, do one of the following:
Before selecting a database, if Use current database is checked, uncheck it.
This option does not apply to Informix SE, for which Use current database must be checked.
Selecting this option adds the Owner/Schema and Object Name parameters to the screen.
If you specify External SQL Scripts in the Restrict Object type to field, these additional fields are displayed.
The following standard naming conventions apply for UNIX, IBM i IFS, and z/OS HFS:
On IBM i, you can use alternative IFS naming conventions to access library members. The following entry illustrates this method:
/QSYS.LIB/MYLIBRARY.LIB/MYSRC.FILE
During synonym generation, the adapter issues native API calls to obtain a list of elements in the select list and builds the Master File with a field for each element. The generated Access File references the location of the SQL script in the DATASET attribute, which contains the full path, including the name and extension of the file containing the SQL Query. For example,
DATASET=/ul/home2/apps/report3.sql
When a WebFOCUS report is created, the SQL Query is used to access data.
Select the Cardinality check box to reflect the current cardinality (number of rows or tuples) in the table during metadata creation. Cardinality is used for equi-joins. The order of retrieval is based on the size (cardinality) of the table. Smaller tables are read first.
If the cardinality of the tables to be used in the application are dynamic, it may not be beneficial to choose this setting.
You can select the Build cluster using foreign keys check box to include within this synonym every table related to the current table by a foreign key. However, this option has been deprecated, as the recommended way to create a cluster is by using the Synonym Editor. The resulting multi-table synonym describes all of the foreign key relationships of this table.
To specify that the Master File created for the synonym should not contain column information, select the Dynamic columns check box.
If this option is selected, column data is retrieved dynamically from the data source at the time of the request.
Only available when External SQL Scripts is selected from the Restrict objects type to drop-down menu. When selected, a SUBQUERY keyword is added to the Access File of the generated synonym. If the corresponding SQL string has valid syntax that can be used in the FROM statement of the generated SQL (what is known as a Derived Table), then the SQL SCRIPT will be processed as a subquery embedded into a FROM clause. This usage allows for more flexibility. For example, the synonym can be used as a target for a JOIN.
If the SQL SCRIPT has parameter markers, such as ? or :, or the syntax contains constructs that are invalid for a derived table, for example ORDER BY, then this keyword should not be selected. At runtime, if SUBQUERY=Y is present and it is determined that the SQL SCRIPT cannot be used in the FROM statement, the setting will be ignored, and a FOC1782 warning message will be issued. The default is selected (SUBQUERY=Y).
Select an application directory. The default value is baseapp.
If you have tables with identical table names, assign a prefix or a suffix to distinguish them. For example, if you have identically named human resources and payroll tables, assign the prefix HR to distinguish the synonyms for the human resources tables. Note that the resulting synonym name cannot exceed 64 characters.
If all tables and views have unique names, leave the prefix and suffix fields blank.
To change the data type mappings from their default settings, select this check box. The customizable mappings are displayed.
Select Create to overwrite any existing synonym with the same fully-qualified name, or Update to synchronize the metadata with an existing synonym. If you select Update, the next screen will show a list of attributes from the DBMS catalog that you can check to allow attributes from the DBMS catalog to override attributes from the existing synonym.
To specify that this synonym should overwrite any earlier synonym with the same fully qualified name, select the Overwrite existing synonyms check box.
Note: The connected user must have operating system write privileges in order to recreate a synonym.
This column displays the name that will be assigned to each synonym. To assign a different name, replace the displayed value.
The user account that created the object or a collection of objects owned by a user.
Is the name of the underlying object.
The object type (Table, View, and so on).
Select tables for which you wish to create synonyms:
An Adapter for Informix synonym comprises a Master File and an Access File. This is a synonym for the table nf29004.
Generated Master File nf29004.mas
FILE=DIVISION, SUFFIX=SQLINF ,$ SEGNAME=SEG1_4, SEGTYPE=S0 ,$ FIELD=DIVISION4, DIVISION4, I9, I4, MISSING=OFF ,$ FIELD=DIVISION_NA4, DIVISION_NA4, A25, A25, MISSING=ON ,$ FIELD=DIVISION_HE4, DIVISION_HE4, I9, I4, MISSING=ON ,$
Generated Access File nf29004.acx
SEGNAME=SEG1_4,TABLENAME=qatst:"edaqa".nf29004, CONNECTION=conn_inf,KEYS=1,$
This chart describes the keywords in the Access File.
Attribute |
Description |
---|---|
SEGNAME |
Value must be identical to the SEGNAME value in the Master File. |
TABLENAME |
Identifies the Informix table name. The table name can be fully qualified as follows: TABLENAME=[[database.]owner.]table |
CONNECTION |
Indicates a previously declared connection. The syntax is: CONNECTION=connection CONNECTION=' ' indicates access to the local Informix database server. Absence of the CONNECTION attribute indicates access to the default database server. |
KEYS |
Indicates how many columns constitute the primary key for the table. Corresponds to the first n fields in the Master File segment. See the KEY attribute below for information about specifying the key fields without having to describe them first in the Master File. |
KEY |
Specifies the columns that participate in the primary key without having to describe them as the first fields in the Master File. The syntax is: KEY=fld1/fld2/.../fldn |
WRITE |
Specifies whether write operations are allowed against the table. |
KEYFLD IXFLD |
Supply the names of the primary key and foreign key fields that implement the relationships established by the multi-table Master File. Together, KEYFLD and IXFLD identify the field shared by a related table pair.
KEYFLD and IXFLD must have the same data type. It is recommended, but not required, that their lengths also be the same. Note: An RDBMS index on both the KEYFLD and IXFLD columns provides the RDBMS with a greater opportunity to produce efficient joins. The columns must have the same data type. If their length is the same, the RDBMS handles the join more efficiently. |
AUTO INCREMENT |
Set to Yes to enable autoincrementing. |
START |
Initial value in incrementing sequence |
INCREMENT |
Increment interval. |
INDEX_NAME INDEX_UNIQUE INDEX_COLUMNS INDEX_ORDER |
Indicate a name of the index in a database, uniqueness, name, and order of the indexed column(s). |
Once you have created a synonym, you can right-click the synonym name in the Adapter navigation pane of either the Web Console or the Data Management Console to access the available options.
For a list of options, see Synonym Management Options.
SQL Data Type mapping options are available in a report available from the Web Console.
For more information, see How to Access the Data Type Report.
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The SET parameter VARCHAR controls the mapping of the Informix data types VARCHAR, VARCHAR2, and NVARCHAR2. By default, the server maps these data types as variable character (AnV).
The following table lists data type mappings based on the value of VARCHAR:
Informix Data Type |
Remarks |
VARCHAR ON |
VARCHAR OFF |
||
---|---|---|---|---|---|
USAGE |
ACTUAL |
USAGE |
ACTUAL |
||
LVARCHAR (n) |
|
A2048V |
A2048V |
A2048 |
A2048 |
NVARCHAR (n) |
|
A255V |
A255V |
A255 |
A255 |
ENGINE SQLINF SET VARCHAR {ON|OFF}
where:
Indicates the adapter. You can omit this value if you previously issued the SET SQLENGINE command.
Maps the Informix data types VARCHAR, VARCHAR2, and NVARCHAR2 as variable-length alphanumeric (AnV). ON is the default value.
Maps the Informix data types VARCHAR, VARCHAR2, and NVARCHAR2 as alphanumeric (A).
The new SQL Expression generator in the TABLE Adapter by default preserves literal contents, including trailing blanks in string literals and the fractional part and exponential notation in numeric literals. This allows greater control over the generated SQL.
In some rare cases when trailing blanks are not needed, the following syntax
ENGINE SQLINF SET TRIM_LITERALS ON
is available to ensure backward compatibility.
You can alter the length and scale of numeric columns returned by a SELECT request to the server by creating different specifications in your login profile or in a stored procedure. The conversion settings are reflected in the Master File in the USAGE and ACTUAL formats of the fields generated by CREATE SYNONYM. This affects how the fields are processed and formatted by the server.
Tip: You can change this setting manually or from the Web Console.
For more information, see Override the Default Precision and Scale.
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