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ASNA DataGate® 7.2 for SQL Server 2005® and SQL Server 2005 Express®
Contents
Connecting to SQL Server on Microsoft’s XP Pro
Service Pack 2
Differences between DataGate, DataGate/400 .NET
(DG/400) and DataGate for SQL Server for .NET
Porting AVR .NET Applications to Employ
ASNA DataGate for SQL Server for .NET
ASNA Visual RPG for .NET Programming
Considerations
ASNA DataGate for SQL
Server 7.2 (7.258.0) now also supports SQL Server 2005 and SQL Server 2005
Express.
DataGate for SQL Server 7.2 employs a new
License Manager that eliminates the duplicate user counts that were encountered in previous versions.
Installing Microsoft's XP Pro Service Pack 2, by default, enables the built-in Windows firewall settings which interfere with SQL Server connectivity. These settings, unless changed, won't let you connect to SQL Server 2000 (with either SQL Server's own Enterprise Manager or with ASNA's DataGate for SQL Server (DSS).
The Windows Firewall closes ports such as 445 that are used for file and printer sharing to prevent Internet computers from connecting to file and print shares on your computer or to other resources. When SQL Server is configured to listen for incoming client connections by using named pipes over a NetBIOS session, SQL Server communicates over TCP ports and these ports must be open. SQL Server clients that are trying to connect to SQL Server will be not be able to connect until SQL Server is set as an exception in Windows Firewall. To set SQL Server as an exception in Windows Firewall, use the steps that are listed here.
·
OpnQryFile caused an exception with multiple
query key fields when Netblockfactor was employed.
·
Copy Library from SQL 2000 to SQL 2005
via Database Manager failed on system objects; however, the data copied
correctly.
As part of the basic strategy to give SQL Server the
semantics of DB2/400, DataGate for SQL Server (DSS) was built
to permit as much manipulation as possible of the underlying objects directly,
via native SQL commands. As a consequence of such strategy, it was decided that
there would be no artificial structure imposed on the tables and views used to
implement the concept of physical and logical files. Files were then
implemented as follows:
·
A
Physical file is implemented as a Table.
An Indexed Physical file requires an Index with the same name as the
Table.
·
A
Simple Logical file is implemented
as a View. An Indexed Simple Logical file requires an
Index with the same name as the View.
·
A
Join Logical file is implemented as
a View. An Indexed Join Logical file requires an
Index with the same name as the View.
This index marks which table is considered the ‘primary file’.
When a simple logical file is created, it is possible to
establish the underlying ‘Select’ in two ways:
·
Select
individual columns from the table.
·
Select
all columns via a ‘Select * from TableX’ by checking
the ‘Clone base file fields in new format’ check box.
In either case, the SCHEMABINDING option is not used; this
permits the table to be altered, thus new columns can be added to an existing
table without having to drop the views first.
However, SQL Server does not reflect the new columns in the
corresponding views (those with the ‘Select * ’ command) until such views are
recreated.
This is a natural behavior of SQL Server views and DSS does
not alter it. Notice also that DSS does not provide a way to add new fields to
a file, so the procedure aforementioned has to be done using SQL Server’s
Enterprise Manager.
Contents
Native SQL Server Field Interpretation
Calling Programs/Procedures Considerations
|
Item |
DG/400 |
DSS for .NET |
DataGate |
|
Library &
file name length |
10 characters |
31 characters |
31 |
|
Members per
file |
0 ® *NoMax |
Exactly 1 |
0 ® *NoMax |
|
File types |
Physical Simple logical Join logical Multiformat logical Print |
Physical SqlLogical Simple logical Join logical Print |
Physical Simple logical Join logical Multiformat logical Print |
|
Max record
length |
32,000 bytes |
8,060 bytes (Not counting Text and Image
fields which are not accessible yet by DSS .NET). |
32,000 bytes |
|
Max number of
records per member |
|
2,147,483,646 |
2,147,483,646* |
|
Library
implemented as: |
Library |
Database |
Illusion |
|
Object text
(description) |
49 characters |
49 characters |
49 characters |
|
Stored
Procedures |
Any AS/400
language |
Programmed in
SQL-Transact |
None |
|
Triggers |
Any AS/400
language |
Programmed in
SQL-Transact |
None |
|
Field Reference
File (FRF) |
A physical file
can refer to any number of FRF, which are any physical file in any library.
However, DG/400 will report only those coming from the file stated in the DDS
REF keyword. |
Refers to the
collection of ‘User Defined Data Types’, which is one per Database (i.e.:
Library). This collection is surfaced
via the special file ‘*FieldRef’ which is the ONLY
file usable as a FRF. |
A physical file
can refer to only ONE FRF, which can be any physical file in
any library. |
* NOTE: For Max number of
records per member, DataGate for Windows and Desktop Servers Release 7.2, Version 7.255 and
higher support member/file sizes limit is 16 exabytes
( 2^4 * 2^60).
|
Item |
DG/400 |
DSS
.NET |
DataGate |
|
Indexed logical files per physical
file |
|
249 |
*NoMax |
|
Logical field used as a key field
must be based on a physical field with the same name |
No |
Yes. Notice that this
eliminates the possibility of using Renamed, Concatenated and Substringed fields as keys. |
No |
|
Maximum number of key fields per key |
|
16 |
250 |
|
Maximum length of key in bytes |
2,000 |
900 |
250 |
Data Access Considerations
|
Item |
DG/400 |
DSS
.NET |
DataGate |
|
Arrival Access |
Relative Record Number is used for
Sequential and Random access. |
Only Consecutive access is supported, but there is no guaranteed order
of retrieval unless the file is indexed.
The only random operation allowed is SetLL
and this is only when used with *Start and *End. No other kind of seeking (SetGT,CHAIN) is allowed. |
Relative Record Number is used for
Sequential and Random access. |
|
Format Name |
Given by file creator. |
Always ‘R’ followed by File Name. Note to AVR Users: The Format can be renamed in the DclDiskFile, using the RNMFMT keyword by providing a new
name, is not necessary to provide the existing Name in the RNMFMT. This
allows the creation of single-source apps that can compile against DG/400 and
DSS .NET. |
Given by File creator. |
|
Open Query File |
Implemented with OpenQry. |
Select expression is used as the
WHERE clause of a SELECT. The key
field list is used as the ORDER BY clause. The select expression is passed directly to the SQL analyzer with no
interpretation. The expression must follow valid SQL Server
syntax. Pay special attention to uses
of logical operators. Use ‘and’ and ‘or’ not ‘&’ and ‘|’. |
A temporary logical file is created
using the select expression as a select/omit expression and the key field
list to define the new key. |
Locking Considerations
Record Locking
DG/400
DB2/400 determines the type and
duration of records locks depending on how the file was opened.
For read-only files, when a record is read, there is no lock requested on it, and if some other application has the record lock, the reading application does not block on the lock, that is, the record gets read in-spite of being locked by somebody else.
For files open for update, every time a record is read it is write-locked so that other updating applications can’t read it. The write lock is held until the record is updated or explicitly unlock by the application or when another record is read or positioned to.
DSS .NET
DSS for .NET (using server cursors) also
determines the locking characteristics bases on how the file is opened.
For read-only files DSS for .NET behaves like DG/400, that is, there are no locks neither placed nor considered on records being read.
The behavior of DSS for .NET when the file is opened for update is similar to DG/400 but with two significant differences: updating a record does not release the lock on the record and explicitly unlocking a record causes the ‘current record position’ to be lost. These differences bear the following considerations.
|
Item |
DG/400 |
DSS
.NET |
|
|
Unlock Record |
Cursor position is unchanged. |
The file has no ‘current’ position
after the Unlock. |
|
|
Update Record |
The record just updated is released. |
The record just updated is kept locked. |
|
|
*NoLock
option on Read operations |
Supported but deprecated. |
Unsupported. The better way to achieve this is to open the file twice, once for input only and the other for update. Where the read appears with the *NoLock option, the file should be substituted with the one open for input only. By doing this, the application can take advantage of network blocking - yielding better performance. |
|
|
Range operations |
When the end of the range is reached, the file has no ‘current’ position. |
When the end of the range is reached, the file has no ‘current’ position. |
|
|
Hit EOF on a ReadE
(P) |
Lose Record position. |
Lose Record position. |
|
|
Other Operations like SetLL |
Unlock Record. |
Unlock Record. |
|
Loops involving SetLL/SetGT
and Read/ReadE/ReadPE should be recoded to use the
Range operations.
The most demanding change is the one requiring segments of code involving CHAIN-UPDATE. Combinations have to be studied and possibly modified.
·
If
the CHAIN-UPDATE happens in a tight loop, then at the end of the loop an UNLOCK
should be issued to release the last record updated. Notice however that the
record position will be lost after the UNLOCK.
·
If
the CHAIN-UPDATE is sprinkled throughout the code, then each case has to be
closely studied.
Object Locking
Not
implemented on DSS .NET.
|
Item |
DG/400 |
DSS
.NET |
DataGate |
|
Field name length |
10 characters |
31 characters |
31 |
|
Types supported |
Char ®
*CHAR Packed ® *PACKED Zoned ® *ZONED Binary ® *BINARY Float ® *FLOAT Integer ® *INTEGER Date ® *DATE Time ® *TIME Timestamp ® *TIMESTAMP Hex ® *HEX DBCS ® *DBCS Unicode ® *DBCS Boolean ®
*CHAR(1) |
Char ®
char Packed ® decimal Zoned ® numeric Binary ® numeric Float(4) ® float Float(8) ® real Integer(2) ® smallint Integer(4) ® int Date ® *ASNA_DSS .NET_DATE
datetime= Time ® *ASNA_DSS .NET_TIME datetime=1899/12/30 Timestamp ® datetime Hex ® binary DBCS ® nchar Unicode ® nchar Boolean ®
Bit |
Char ®
*CHAR Packed ® *PACKED Zoned ® *ZONED Binary ® *BINARY Float ® *FLOAT Integer ® *INTEGER Date ® *DATE Time ® *TIME Timestamp ® *TIMESTAMP Hex ® *HEX DBCS ® *DBCS Unicode ® *DBCS Boolean ® *CHAR(1) |
|
Allow Nulls |
Yes |
Yes |
No |
|
Variable Length Fields |
Char Hex DBCS |
Char ® varchar Hex ® varbinary DBCS ® varnchar |
No |
|
Date value range |
|
Datetime (ASNA_DSS .NET_DATE): 1753-01-01 ® 9999-12-31 Smalldatetime: 1900-01-01 ® 2079-06-06 |
|
|
Decimal Number Storage |
Packed (1 nibble per digit) Zoned (1 bye per digit) Binary: 1 – 4 digits = 2 bytes
5 – 9 digits = 4 bytes |
Decimal | Numeric: 1 – 9 digits = 4 + 1 bytes 10 – 19 digits = 8 + 1 bytes 20 – 29 digits = 12 + 1 bytes 30 – 38 digits = 16 + 1 bytes |
Packed (1 nibble per digit) Zoned (1 bye per digit) Binary: 1 – 4 digits = 2 bytes
5 – 9 digits = 4 bytes |
|
Date storage |
1 byte per digit/character |
Datetime 8 bytes ASNA_DSS .NET_DATE 8 bytes SmallDatetime
4 bytes |
1 byte per digit/character |
|
Fields per file |
|
1,024 |
32,000 |
|
Re-typing logical fields |
Unrestricted |
Logical fields who’s type differs from that of the corresponding
physical field cannot be updated. |
Unrestricted |
|
Column Heading Definitions |
Up to 3 31-characters |
The 3 headings are concatenated into
the MS Access CAPTION field. |
Up to 3 31-characters |
|
Text Description |
Up to 49 characters |
Up to 49 characters |
Up to 49 characters |
|
Numerics |
Date/Time |
Char/Other |
|
Float ®
*Float (4) Real ® *Float (8) Int ® *Integer (4) SmallInt ® *Integer (2) TinyInt ® *Integer (2) Decimal ® *Packed BigInt ® *Zoned(19,0) Money ® * Zoned(19,4) Numeric ® *Zoned SmallMoney ® * Zoned(9,4) |
DateTime ®
*Timestamp SmallDateTime ® *Timestamp |
Bit ®
*Boolean Char ® *Char VarChar ® *Char (VarLen) NChar ® *Unicode NVarChar ® *Unicode (VarLen) Binary ® *Hex VarBinary ® *Hex (VarLen) UniqueIdentifier ® *Hex (16) |
The types Image, Text and NText are not supported.
Fields of these types are hidden from the file definition. You will be able to display the file
definition in Database Manager, but won’t be able to open the file. To ensure
future application compatibility, you should not use files containing these
field types. Instead you should create logical files naming the
individual fields that your application will manipulate. That way, if in
a future release the fields ‘appear’, your application will not break.
|
Item |
DG/400 |
DSS
.NET |
DataGate |
|
|
Supports Use Default for Joins by: |
DDS Keyword JOINDFLT?? When a record is not found in the
secondary file, logical fields whose base is that file will be populated with
the default values specified in the physical file definition. |
|
|
|
Creating
a Left Outer Join instead of an Inner Join.
From SQL Docs:
LEFT JOIN or LEFT OUTER JOIN
|
The result set of a left outer join includes all the rows from the left table specified in the LEFT OUTER clause, not just the ones in which the joined columns match. When a row in the left table has no matching rows in the right table, the associated result set row contains null values for all select list columns coming from the right table.Yes |
|
||
|
Supports ‘Join Duplicates By’ |
DDS Keyword JDUP |
Not supported.
Duplicate rows in the ‘secondary’ tables may be returned in random
order. |
Yes |
|
Item |
DG/400 |
DSS
.NET |
DataGate |
|
Maximum Number of Parameters |
36 |
2100 |
N/A |
|
Parameter Direction |
*Input, *Output, *Both |
*Input, *Both |
N/A |
FAQ
Q. Will DataGate for SQL Server require SQL
Server client licenses for end Users or will a server license be
enough?
A. Every user will have to be licensed. There are 2 ways of achieving this; one is to
buy individual Per-Seat licenses, the other is to buy a per-processor license.
The following link will take you to the MS prices as of Aug. 2001:
http://www.microsoft.com/sql/howtobuy/pricing/default.asp. This is another good link with common
licensing questions:
http://www.microsoft.com/catalog/display.asp?site=10145&subid=22&pg=4
Here is a breakpoint list of the 2 different
license models for Standard Edition:
SQL Server 2000 Standard
Edition - purchase processor license if:
1 processor machine: more than 24 users
2 processor machine: more than 53 users
4 processor machine: more than 112 users
8 processor machine: more than 229 users
Q. Will I have to get a DataGate for
SQL Server license or is a SQL Server licenses all I need?
A. You will have to obtain a DataGate license to
access data stored in SQL Server.
Q. Which version(s) of SQL Server will be
supported by DataGate for SQL Server?
A. DataGate supports all editions of SQL Server 2000 (
Q. Is the Library List supported?
A. Yes.
Q. I have an DataGate database with files in the
root library, how can I get them into SQL Server?
A. Use the CopyLibrary option of
DataGate Database Manager, user ‘/’ for the Source library and a named
library for the target.
Q. After copying my libraries to SQL Server, are there
new files identical to the originals?
A. Almost, but not quite. The main difference you will see
is that fields defined as BINARY in the original files will appear as being
ZONED. The impact of this change in your
AVR programs is only reflected when the field is part of a Data Structure, in
which case, the compiler will protest the discrepancy in the definition of the
field, i.e: the program defines as binary, but the
file as defines as zoned.
Q. What is MSDE ?
A. Go to http://www.microsoft.com/sql/techinfo/development/2000/MSDE2000.asp for a description of MSDE. The
Addendum 1 is attached in case the link moves.
Q. Given that DSS for .NET imposes the format name
(as an ‘R’ followed by the file name), do I have to modify all of my file
record formats on the AS/400 to match the file and how will this affect my AVR
programs when referring to the old format name?
A. If you compile against DataGate or DG400, you
will be able to run against DSS for .NET even if your format names are
different. However if you compile
against DSS for .NET and your code refers to a format name which doesn't match
the one in DSS .NET, then you can either change your references to it (lots of
work), or do a rename format in the DclDiskFile
(little work).
RNMFMT has been enhanced to take a single parameter
to indicate to AVR that this is the new name by which you will be referring to
the ONLY format in this DclDiskFile. If you don't rename the format, then AVR will
use whatever the database provided it with.
Q. How are the printer files going to work if we
cannot have multiple record formats?
A. Print files are supported just like in DataGate,
that is, they can still be multi-format.
It is only the data files that have to be single-format.
Porting AVR .NET Applications to Employ
ASNA DataGate® for SQL Server®
for .NET
Contents
4. Optimize Your Applications with
New Op-Codes:
New Error Conditions under DSS for .NET
ASNA's DataGate for SQL Server Classic (DSS for .NET) provides AVR programmers’ access to Microsoft SQL Server 2000 through native RPG file IO using familiar RPG operation codes such as CHAIN and SETLL. DSS for .NET allows you write one set of applications that works concurrently with both the iSeries and SQL Server databases.
You will not need to learn SQL to get effective access to SQL Server. The skills you use today for iSeries file IO will work exactly the same way for SQL Server via DSS for .NET. The same AVR programs that connect to SQL Server will seamlessly connect to the iSeries and ASNA’s DataGate engine.
DSS for .NET makes a SQL Server instance appear as a database similar to DataGate or iSeries. The characteristic features of DB2/400 materialize on SQL Server when seen through the eyes of DSS for .NET. With DSS for .NET, you can use the Library list, Physical and Logical files, even DB2 field types, like packed and zoned.
Back to Porting Applications Top
Even though DSS for .NET tries to make SQL Server look like DB2/400, there are several features that cannot be implemented in a totally transparent fashion. The SQL Server 2000 database engine is of a different design and implementation than the iSeries and DataGate engines.
The intent of this document is to help you become aware of the items that will most likely affect your application and the process of using SQL Server as your database. Through it all, remember the goal you are seeking is to create applications that take advantage of the many features of SQL Server and to create applications that can run with either SQL Server or DB2/400 as the underlying database engine.
In the next sections we’ll deal with all of the issues that will need your attention, but the following items are probably the ones with the most impact for many of you.
No Multi-Format Logical Files:
DSS for .NET implements a physical file through the use of a native SQL Server table. A logical file is implemented through a native view. SQL Server Views are single formatted in nature, so there is no support for multi-format logical data files. You will have to eliminate any reference to multi-format logical files in your application.
Print files, although they are typically multi-formatted, are fully supported in DSS for .NET, however.
Single Member Files:
SQL Server doesn’t have the concept of members of a table/view. DSS for .NET makes it appear as though each file had one (and only one) member; the member name is exactly the same as the file name. For the member name, you can use the exact name or the special values *FIRST and *FILE. You should be careful when using the Copy Data and Copy Library tools of the DataGate Database Manager to copy a file from DataGate or iSeries, because they default to *SAME for the target member name; if the source member name was differently than the file name the copy will fail.
If your application depends on the existence of multiple members per file, you will want to re-architect it to provide an alternative method for handling the logic involving these files.
Logical Field Restrictions:
There are two restrictions on the usage of logical
fields when they change the name or the type of their corresponding base
physical field. When the field is
retyped, most typically because the field is a concatenation or substring of
the physical, then the field becomes read only.
A logical field, whose name has changed from its physical base field, can’t
be used as a key field in the logical file.
No Qtemp:
Version 5.0 of DSS for .NET does not support the
special library QTEMP.
Unlocking Records:
This is probably the most demanding area of application adaptation between the differences of implementation between iSeries method of record locking and that of the SQL Server database engine. The problem arises in two areas: Using the *nolock keyword on the read operations and on the implementation of the UNLOCK command.
DSS for .NET uses SQL Server ‘Server Cursors’ to implement file access. When a file is opened for update, it is not possible to tell SQL Server to not lock the record on a read, so a read with *nolock has no effect for files opened for Update. There are two methods to resolve this problem:
1.
Declare a second instance of the file marked as input only
and use it wherever the NoLock option would have been
given on a read/chain.
2.
Retain the *nolock and follow the
read/chain with an UNLOCK command. Be
aware this method imposes some restrictions as stated in the next paragraph.
The UNLOCK command leaves the cursor in a no-position state, meaning you can’t perform a subsequent read (next/previous) without repositioning the file with a SETLL, SETGT or CHAIN.
Back to Porting Applications Top
In a nutshell, the process of upgrading your application is composed of the following steps:
1. Get a decent size computer.
2. Move your data from the iSeries or DataGate Engine to SQL Server.
3. If necessary, modify your application to adapt to any new restrictions.
4. Optimize your application to take advantage of the new AVR op-codes.
1. Computer Size
SQL Server is very demanding on computer resources. We recommend you get a computer with at least the capacity of the cheapest machine you can get from Dell, but with twice the amount of memory. The machine doesn’t have to be a Dell computer, but use the Dell machine as a reference to configure your box.
One more thing, we highly recommend that you use Windows XP Professional or Windows 2000 workstation for your development machine.
Back to Porting Applications Top
2. Move Your Data
The first step after installing DataGate for SQL Server on your machine is to create a Database Name that points to your SQL Server. You can use the Database Wizard or the Work with Database Names option of the Database menu of Database Manager.
Under typical SQL Server installations, there is only one instance of the server installed on the machine and that instance typically contains the following databases:
· Master
· Model
· Msdb
· Northwind
·
Pubs
· Tempdb
Each one of these databases will be presented through DSS for .NET as individual libraries. Since all databases are shown under a common database name, the "Label' parameter of a database name pointing to DataGate for SQL Server 7.2 must be "SQL".
The following figure shows a Database
Name called
You can use *DOMAIN for your user name or you can supply one of the login names recognized by SQL Server with its corresponding password.
Test your Database Name by opening the database with Database Manager. You should see something like the following:
When you open a database for the first time, Database Manager prompts you for your viewing preferences for the database with a dialog like the following.
Notice in particular the checkbox Show system objects. It controls whether to or not to display a set of SQL Server objects called sysxxxx. For iSeries databases, this option shows or hides objects like QSYS.
Prepare Files and Copy Libraries:
The next step in moving your data is to prepare a
library (or libraries) on the source machine with all the files you wish to
copy to the target SQL Server.
After you have prepared the library, use the Copy Library option from the Tool menu to move the data.
You can use one of your existing libraries, but it
may require some clean up before it is ready. To check your data, use one of
the options below:
1.
You
can do a visual inspection of the files in the library to
verify/modify them to comply with the check list.
2.
Alternatively
issue the copy command and wait for it to tell you whether
there are any problems.
Visual Inspection Using a Checklist:
Use the following checklist to ensure a DataGate or iSeries data file will be successfully copied to SQL Server:
The file must have:
· only one member
· the member name the same as the file name
· only one format
·
maximum of 16
key fields
·
maximum key
length of 900 bytes
·
maximum of 1024
fields
·
maximum record
length of 8060 bytes
Logical files have extra
restrictions. Make sure that the key
fields are not substrings or concatenations of physical fields and that the
name of the logical field is the same as that of its base field.
Issue the Copy Command and Note if there are any Problems
If you choose the second option, uncheck the Copy Data Records in the Copy Library dialog to speed up the process. Take note of any problem and after fixing it, delete the target library and issue the Copy Library command again, this time copying the data records. You can view the result of the copy in the Message Log window.
Once you have modified your files to comply with the limitations stated above, you can use the Copy Library menu option.
All files stored under SQL Server must reside inside a ‘Library’ just like files on an iSeries. DataGate Engine has allowed files to be placed at the ‘root’ level of the database and under subfolders inside a library. If you have files in places other than first level libraries, you’ll have to adapt your application (or the library list) to point to the new locations.
When a physical file is copied to SQL Server, a table is created with the name of the physical file. For logical files, a view is created. In either case, if the file is keyed, an index is created on the table; for logical files the index is created on the primary base table.
When a view is encountered through DSS for .NET, it is
reported as being a new kind of logical file, called SQL Logical. That is why when a logical file is copied, regardless
of whether a logical file is a Simple
Logical or a Join Logical, it will appear on the SQL Server database as a SQL Logical file.
Field Reference Files are used on the iSeries to collect definitions of named field types that are used in the creation of data files. SQL Server has a built-in data dictionary where user types can be defined. DSS for .NET surfaces this data dictionary through the special file *FieldRef. There is one *FieldRef file per library.
If you use a field reference file as part of your data file definitions, you should first import those fields into the data dictionary of the DSS for .NET library.
Follow these steps to populate the dictionary:
1.
Open
the source database.
2.
Drag
the field reference file to the Work
Definition Area.
3.
Open the target database.
4.
Create
the target library.
5.
Drag
the field reference file to the target database taking care of specifying *FieldRef as
the file name to be created. DSS for .NET will notice the special name and add
the fields to the data dictionary.
After you have populated the data
dictionary, you can view the type definitions by clicking on the *FieldRef file in the target library.
If you don’t see the *FieldRef file in the library, ensure that the option to Show System Objects is checked ON in the options dialog.
Back
to Porting Applications Top
3. Adapt the Application
Enable DataGate for SQL Server Warnings:
To assist in finding areas in code that will potentially cause an error, a new IDE option has been added to ASNA Visual RPG to give warnings for invalid operations under DSS for .NET. This option is located within the “Compiler” Tab of the Project >Settings menu option.
Select the Enable DataGate for SQL Server Warnings option so that a check mark appears in the check box and select OK.
Change your DCLDISKFILE Statements:
Depending upon your application, the following are some changes you will/may need to make to your DCLDISKFILE statements.
Arrival sequence processing must be changed to indexed processing. SQL Server doesn’t have the concept of a relative record number (RRN).
The simplest method for handling this would be to employ the use of a key field in the file. If the file is being processed only in consecutive fashion (i.e. you don’t use random op-codes like SETLL or CHAIN on the file) then you can choose any field to be the key and specify RANDOM(*NO) in the DCLDISKFILE. If you do process the file randomly, then you will need to add a field to the file to simulate the RRN sequence. The easiest way to achieve this is by adding an identity field called RecNum of type integer.
In DSS for .NET, the record format name is always “R” + Filename. If the record format name is anything else, and you’ve specified this record format name on I/O operations, a rename format will need to be specified on the DCLDISKFILE statement as follows. RNMFMT(OldFormatName) where OldFormatName is the name of the existing format. No changes will need to be made to the actual I/O statements.
If your application makes use of the Open Query File capability of DataGate or iSeries, you will have to take care of a couple of things.
§ The string passed in the QrySelect must comply with the syntax of SQL Server, for example you should use the word ‘and’ not the symbol ‘&’.
§ If you are changing the order of the file by providing a value in the QryKeyFlds parameter, then you must also specify RANDOM(*NO) in the DCLDISKFILE to state that you will be accessing this file only consecutively.
If an application is going to run against both DSS for .NET and DataGate 400, and your file currently contains binary fields, you will need to consider changing the field type.
The behavior of DSS for .NET when the file is opened for update is similar to DG/400, but with two significant differences:
1. Updating a record does not release the lock on the record.
2. Explicitly unlocking a record causes the ‘current record position’ to be lost.
These differences bear the following considerations:
Loops involving SetLL-SetGT and Read-ReadE-ReadPE should be re-coded to use the Range operations.
The most demanding change is the one requiring segments of code involving CHAIN-UPDATE combinations to be studied and possibly modified.
·
If the CHAIN-UPDATE happens in a tight loop, then at the
end of the loop, an UNLOCK should be issued to release the last record updated. Notice however that
the record position will be lost after the UNLOCK.
· If the CHAIN-UPDATE is sprinkled throughout the code, then each case has to be closely studied.
Back to Porting Applications Top
4. Optimize Your Applications with New Op-Codes
To optimize SQL Server processing
and to enhance client/server performance with all supported database engines
(iSeries/400, DataGate and SQL Server) with dynamic Network Blocking, AVR 4.0
introduces three new op-codes; SetRange, ReadRange and DeleteRange, as
described below:
New I/O
op-codes provide better performance in two ways:
1.
When
working with large SQL Server files,
DSS for .NET is able to optimize the record set selection
operation.
2.
Network
Blocking becomes dynamic, in that records outside of the range are not transmitted to the client.
Use the SETRANGE op-code in
place of SETLL and SETGT when you’re doing SETLL/READE
and SETGT/READPE loops.
Use the READRANGE op-code in
place of the CHAIN op-code when you’re doing
CHAIN/READE loops.
Use the DELETERANGE in place
of DELETE loops.
Strong consideration should be given to Visual RPG Error
Indicators when performing I/O operations as they could be turned on now for reasons
not present before. For instance, when the Chain opcode
returned an error, the cause was commonly assumed to be that the record was
busy. With DSS for .NET, error indicators can be turned on for various
reasons such as the use of the *NOLOCK option on I/O operations. (See Locking Considerations in
the DG400 vs. DSS for .NET document).
New Error
Conditions under DSS for .NET:
The following situations will cause the error indicator to
be set on.
1.
Arrival Random Access.
When a file is opened for *Arrival
access, commands such as Chain, Setll, etc, will
cause an error condition.
2.
Use of the *NOLOCK option is not supported under DSS for .NET.
Any I/O operations that make use of
the *NOLOCK option
when working with files opened for update will cause an error condition.
ASNA Visual RPG® for .NET Programming Considerations
Contents
Considerations for Adapting
Existing Applications to DSS for .NET
Strong consideration should be given to Visual RPG Error
Indicators when performing I/O operations as they could be turned on now for
reasons not present before. For instance, when the Chain opcode returned an error, the cause was commonly assumed to
be that the record was busy. With DSS for .NET, error indicators can be
turned on for various reasons such as the use of the *NOLOCK option on I/O
operations. (See Locking
considerations in the DG400 vs. DSS for .NET document).
Back to Programming Considerations
The following situations will cause the error indicator to
be set on.
1.
Arrival Random Access.
When a
file is opened for *Arrival access,
commands such as Chain, Setll, etc, will cause an
error condition.
2.
Use of the *NOLOCK option is not supported under DSS for .NET.
Any I/O operations that make use of the *NOLOCK option when
working with files opened for update will cause an error condition.
To assist in finding areas in code that will potentially cause an error, a new IDE option is added to give warnings for invalid operations for DSS for .NET. This option is located in the “Compiler” Tab of the Project >Settings menu option.
Back to Programming Considerations
New Range Opcodes
New I/O op codes provide better
performance when working with large files.
·
SetRange – Use the SetRange
opcode in place of Setll
when you’re doing Setll/Reade
loops.
·
ReadRange – Use the ReadRange
opcode in place of the Chain opcode
when you’re doing Chain/Reade loops.
·
DeleteRange – Use the DeleteRange
when performing delete loops.
Back to Programming Considerations
In DSS for .NET, the record format
name is always “R” + Filename. If
the record format name is anything else, and you’ve specified this
record format name on I/O operations, a rename format will need to be specified
on the DCLDISKFILE statement as follows. RNMFMT(OldFormatName)
where OldFormatName is the name of the existing
format. No changes will need to be made to the actual I/O statements.
The old syntax of RNMFMT(OldFormatName,NewFormatName) is not needed.
·
Arrival sequence processing must be changed to indexed processing. The simplest method for handling this
would be to employ the use of a key field in the file.
·
If
you’re using multi-member files, you will need
to provide an alternative method for handling the logic involving these files.
·
If
your file’s record length is > 8060, you will need to consider
changes necessary in order to make the record length smaller.
·
Be
sure to include the range operations to enhance speed.
·
If
you were using the *NOLOCK opcode for files
opened for update, you will need to declare an *Input instance of the
file for *NOLOCK access.
·
If
an application is going to run against both DSS for .NET and DataGate 400, and
your file currently contains binary fields, you will need to consider
changing the field type.
Back to Programming Considerations
·
Qtemp
·
Object
Locking
Back to Programming Considerations
·
It
is recommended that you do not use ADBFEDIT to browse files that are not
indexed because of the inability to scroll within the file.
These types of files can be viewed with
SQL Server’s Enterprise Manager.
Back to Programming Considerations
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10/24/2007
© 2007.
Amalgamated Software of
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