CodeBase 6 Hints

This document provides a list of solutions for common problems and answers to frequently asked  questions.

Common problems

• Visual C++ 6 support
• Windows 98 GPF during installation
• Windows NT
• Novell and Windows
• Overflow Error calling report4parent()
• Unresolved External Symbol operator new
• CodeUtil
• beginthread Error Building DLL
• Frequent Index Corruption under Windows 95
• UNIX bus errors or core dumps
• Link Error: LIBCI.LIB cannot be found
• CodeBase not working after error
• Invalid Transaction file (error -1210) when opening file
• Class not registered. Looking for object with CLSID: {...}
• Exceeding the 64K default data segment limit in a DOS application
• Structure Verification Failure (error -960) when using CodeBase 6.5 and C++Builder 4 or 5
• Design-time license error when using CodeControls
• "Specified driver could not be loaded due to system error 127 (CodeBaseOdbcStand)"

Frequently Asked Questions

General CodeBase questions

• What files are used by CodeBase?
• What is the difference between opening a file in read-only mode, and opening the file in exclusive mode?
• How can files be opened in different modes?
• I get an error after opening several files simultaneously. However, if I first close some files, and then open the rest, everything is fine.
• When I change my database on one workstation, why do the changes not appear on another workstation and I receive errors?
• What is a BLOB?

Indexes and Seeking

• How do I seek for a Unicode string?
• How do I seek for a value in a DateTime field?
• What is the difference between a TAG and an INDEX?
• What is a .CGP file?
• How do I perform an exact match?
• How can I perform a case-insensitive search?
• How can I get the number of records that an index contains?
• How do I create a tag consisting of two numerical fields?
• How can I filter out deleted records when browsing a data file?
• When reindexing a database, why does the index file shrink dramatically?
• How are indexes in a non-default directory and indexes with non-standard name extensions used with CodeBase?
• Why are all unique tags set to r4uniqueContinue, even though they were created with the r4unique option?
• Why is my r4uniqueContinue tag not properly updated?

Queries, Relations, and Expressions

• What are the criteria for Query Optimization technology to be activated?
• Why can Query Optimization not use a r4uniqueContinue tag?
• Why are some slaves in a relation set blank?
• When a query that uses Query Optimization technology (QO) is made, how is it possible to find out the number of records that are returned?
• How is a query with a date field made?
• How do I shorten an expression with code4calcCreate?
• How can fields from different files be referenced in a query?
• Why do I have trouble with relations when I am using two files that have the same name, even if they are in different directories?
• Is it possible to have a master file with multiple relations to the same slave file?
• What is code4calcCreate() used for?
• How can fields be concatenated (linked together) into a meaningful expression?

Performance

• When I append many records to file, why does performance gradually degrade after the first few hundred records?

Client/Server

• How can I ensure optimal performance of the CodeBase database server?
• How do I know what host name to pass to code4connect()?

CodeReporter

• Can I speed up the time it takes to display a sorted report?
• How is it possible to calculate a total without showing it on the screen?
• How do I re-compile any of the launch utilities?
• Why are all reports printed from DOS double spaced and have extra blank pages in the middle and end?
• How can I make my report page size on screen identical to the sheets I use for my printer?
• After viewing one report with an invalid printer driver, why do subsequent reports also appear blank?

Other CodeBase Errors

• Error Number: -1 or e4codeBase
• Error Number: -20
• Error Number: -30
• Error Number: -310
• Error Number: -440
• Error Number: -910
• Error Number: -930
• Error Number: -1210

 

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Common problems

Visual C++ 6 support

Visual C++ 6 will work with the pre-built CodeBase 6.4 DLLs.

Visual C++ 6 may generate compile errors when rebuilding the CodeBase static library or DLL. If this occurs, download these fixed CodeBase 6.4 source files and place them in your SOURCE directory.

Visual C++ 6 will work with CodeControls 3, but the example projects for Visual C++ 5 that come with CodeBase 6.4 will not work with Visual C++ 6. These example projects have been updated for Visual C++ 6.

Two example source files will not compile with Visual C++ 6. These example source files have been updated to work.
 

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Windows 98 GPF during installation GPF

A GPF can occur while running the CodeBase 6.4 install program. It occurs when the Browse button in the "Choose Destination Location" window is pressed. There are two solutions to this problem:

1. Restart the computer and run the installation program again before running any other programs. Do not click the Browse button; you will not be able to modify the directory CodeBase is installed to.
2. Copy the files directly from the CD. The files on the CD are not compressed, so they can be copied directly to your hard drive. Stand-alone support can be found in the CB64 directory, and client/server support can be found in the CB64CS directory. NOTE: If you wish to use CodeControls, you will have to manually register the OCX files with REGSVR32.EXE.

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Windows NT

Novell and Windows

Overflow Error calling report4parent()

When compiling with Microsoft Visual C++, the following error might be generated:
libcimtd.lib(iostrini.obj) : error LNK2001: unresolved external symbol "void * __cdecl operator new(unsigned int,int,char const *,int)"
This is caused by using the wrong run-time library. For the Release configuration, use the Multithreaded run-time library. For the Debug configuration, use the Debug Multithreaded run-time library.

NetBEUI

CodeUtil

beginthread Error Building DLL

Frequent Index Corruption under Windows 95

UNIX bus errors or core dumps

Link Error: LIBCI.LIB cannot be found

CodeBase not working after error

Invalid Transaction file (error -1210) when opening file

Class not registered. Looking for object with CLSID: {...}

Exceeding the 64K default data segment limit in a DOS application

This error can sometimes be resolved by re-building the CodeBase client library with the E4OFF_STRING compiler switch. This should free up approximately 40K in your default data segment. With this switch set, CodeBase error messages will only output error numbers, without any text information about the error. You can cross reference the error message by looking up the error numbers in E4STRING.C.

Structure Verification Failure (error -960) when using CodeBase 6.5 and C++Builder 4 or 5

This is due to a difference between the compiler options used to build the CodeBase libraries, and the ones you are using to build your application under C++Builder.  Specifically, the CodeBase libraries are compiled use the -b compiler option, which causes the compiler to make enumerated data types integer-sized.  However, projects created by C++Builder use the -b- compiler option by default, which makes enumerated data types byte-sized.

Under C++Builder 4, use the Project|View Makefile menu command to examine the makefile for your project. In the makefile, there is a variable called CFLAG1 that is assigned several compiler options. Change the -b- option to -b, and save the makefile.

Under C++Builder 5, use the Project|Options menu command, and go to the Compiler tab.  Under the Compiling section, check the box besides "Treat enum types as ints" and click the OK button.

Design-time license error when using CodeControls

There are two common causes of this error:

1. The CodeBase Administrator was installed or re-installed after the installation of the CodeControls.  This results in the CodeBase Administrator's set of CodeControls, which does not have a design-time license, to be registered, overwriting the registration of the CodeControls with the design-time license.  The CodeControl OCX files in the \CodeBase\CodeCtrl directory must be re-registered using the instructions on page 190 of the CodeControl 3 manual.
2. The CodeBase 6.5 CodeControls were registered with the wrong set of design-time license files.  The correct set of license files can be downloaded from here to replace the existing ones in the \CodeBase\CodeCtrl directory, and then the CodeControl OCX files can be re-registered using the instructions on page 190 of the CodeControl 3 manual.

"Specified driver could not be loaded due to system error 127 (CodeBaseOdbcStand)"

The current releases of the stand-alone CodeBase SQL/ODBC Driver (not the CodeBase Reduced SQL/ODBC Driver) use their own version of the c4dll.dll.  However, the installation program for the driver will not install its c4dll.dll over any pre-existing c4dll.dll in the \Windows\System or \WinNT\System32 directory.  The c4dll.dll that is currently in the \Windows\System or \WinNT\System32 directory must be removed, then the stand-alone CodeBase SQL/ODBC Driver must be un-installed and re-installed.

Frequently Asked Questions

What Files are used by CodeBase?

 

Description	File Extension
	FoxPro	dBASE IV	Clipper
Data File	DBF	DBF	DBF
Memo File	FPT	DBT	DBT
Index File	CDX	MDX	CGP, NTX

Data File: A file with the DBF extension. It contains all the non-memo entries.

Memo File: A file with either a DBT or FPT extension. It contains all memo entries.

Group File: A file with a CGP extension. This file is unique to CodeBase and is used only in the Clipper case. It contains the names of the index files.

Index File: A file with a CDX, MDX or NTX extension. This file contains the sort order of the data file.

For further information about the contents of the above files, please consult other questions in this document or the User's and Reference Guides.

What is the difference between opening a file in read-only mode, and opening the file in exclusive mode?

When a file is opened in read-only mode, other processes may have opened the same file at the same time. When a process opens the file in exclusive mode, no other processes may have open the same file at the same time. Also, no file locks are made. Opening a file in exclusive mode yields faster access times, and prevents other applications from accessing the file.

How can files be opened in different modes?

Suppose that we want to open four files using different modes:
 
 
 
 
 
 

File Name Access Mode Read Only FILE1.DBF Fully Shared FILE2.DBF Exclusive   FILE3.DBF Deny Others Write   FILE4.DBF Fully Shared

In order to do this, we need only change the CODE4 member values. In this particular case, the significant members are:  CODE4.readOnly  CODE4.accessMode

I get an error after opening several files simultaneously. However, if I first close some files, and then open the rest, everything is fine.

You are running into an O/S limitation. Refer to the explanation for Error -20 and Error -30.

See Also: Error -20, Error -30

When I change my database on one workstation, who do the changes not appear on another workstation and I receive errors?

CodeBase, DOS and Windows sometimes buffer their output data. Therefore, when one application makes changes, the second may not be 'aware' of them since they were not flushed to the disk. In order to overcome this 'optimization,' the programmer must FLUSH the changes made. Although the process may be much more involved, the above advice will get you started.

Why do I have trouble with relations when I am using two files that have the same name, even if they are in different directories?

This is because the two files have the same alias. An alias is the 'name' that CodeBase associates with a file. By default this 'name' is the same as the name of the file. Thus a file called FILE.DBF will, by default, have the alias 'FILE.'  In order to get the name of the alias, you must make a call to d4alias. You may change the alias of any file with the d4aliasSet command. Thus, in order to open two files with the same name, you must open the first, change its alias, and only then open the next file.

Let us assume that we have two files called C:\DIR1\FILE.DBF and C:\DIR2\FILE.DBF. Click below for a short program segment that will open both files.

See also: Error -910

What is a BLOB?

ALL memo fields are considered as binary large objects (BLOBs) under the 'official' definition, as provided by Borland (BLOB is a registered trademark). However, the BLOB concept is usually reserved for memo fields that are larger than 64k.

The following information should be understood when using memo fields:

1. S4CLIPPER memo fields can not store the '1A' character in any of their contents. This character is used to indicate the 'end of memo entry.'  This is because the length of the memo is not stored explicitly. If the '1A' character must be stored in the memo field then it will be necessary to create a character sequence to denote it implicitly. However, each programmer must write their own routine since a standard convention does not exist.
2. The size of the memo entry is not inherently limited to a specific size by the memo type format. However, the largest possible memo entry is always the maximum value of an 'unsigned integer.'  Thus, the size of the memo entry is compiler dependent; this is summarized in the following two points:
• The size of an unsigned integer in a 16 bit compiler is two bytes. Therefore, the maximum memo entry may be as large as 64k bytes (2^16) long.
• The size of an unsigned integer in a 32 bit compiler is four bytes. Therefore, the maximum memo entry may be as large as 4G bytes (2^32) long.
3. When a 16 bit CodeBase application encounters a memo entry that is greater than 64k bytes while compressing a memo file, it will correctly compress the memo entry. It does this by performing segmented partial reads on the memo file.

If I search for the string "JOHN", I get a return code of 0 (r4success in Appendix B), yet I am positioned on record "JOHNSON". How do I perform an exact match and find only "JOHN" ?

Let's assume that your field can store seven characters, i.e. you defined it as "FIELD_NAME", r4str, 7, 0. When a seek is performed on "JOHN", CodeBase looks for the first occurrence of "JOHN". This may be found in "JOHNSON". When you store "JOHN", xBASE (which includes CodeBase) stores the value as "JOHN " (that is JOHN with three trailing spaces). Therefore, if you want to do an "exact" seek to find JOHN, you will have to pass " JOHN  " to the seeking command.

How can I perform a case-insensitive search?

In this case, you do not change searching method; rather, you must change your indexing strategy. If you use the index expression: "UPPER(field_name)" then a search for "JOHN" will be case-insensitive: both "John" and "jOhN" will be found.

What is the difference between a TAG and an INDEX?

A tag represents a particular sort order of the records in the database. An index is a file on disk that stores one or more tags.

Suppose we have a database with two fields, NAME and ID. If we want to sort the database according to the NAME field then we set up a TAG (sort order) based on the NAME field. Similarly, if we want to sort on the ID field we can create a TAG based on the ID field. If we want to search and skip through the database using the alphabetized name tag, we must select the NAME tag using the "tag select" command. We may do the same for the ID numbers.

In order to store the TAGs on disk, xBASE (which includes CodeBase) uses INDEX files. CDX and MDX INDEX files may contain several tags. However, NTX INDEX file only contain a single tag. Once we open an INDEX file, we have access to all the tags that are associated with the index.

When I try to open my DBF, I get an error #-60: "Unable to open XXX.CGP."  What is a .CGP file?

To get a complete answer first read the question: What is the difference between a TAG and an INDEX.

Also, please refer to "Group Files" in the CodeBase manuals.

CGP files are unique to CodeBase and exist only in the cases when S4CLIPPER is defined.  Because Clipper (NTX) does not have multiple-tag index files, CodeBase implements a CGP file which emulates this functionality. A CGP file allows you to open your NTX files as if they are a part of a multiple index. For instance, if you have two NTX files called TAG1.NTX and TAG2.NTX, you may either open each individually, or use a CGP file and open the two files as if they were a single index file. Below is an example CGP file that contains a reference to the above index files:
 

TAG1
TAG2
By inspection it becomes obvious that the CGP file is simply a text file that contains the names of the tags used by the data file. When a data file is opened, CodeBase automatically attempts to open the associated CGP file so that it will be able to open the separate index files. If the CGP file does not exist then a -60 error will result. Therefore, in order to avoid the aforementioned error, set CODE4.autoOpen variable to 0 (OFF), before opening the data file.

If a CGP file is not used then each index file must be opened manually. Refer to the example programs NOGROUP1 and NOGROUP2 in the User's Guide.

How are indexes in a non-default directory and indexes with non-standard name extensions used with CodeBase?

CodeBase is able to create index files in a non-default directory. In order to do so, the index file must be created with a separate call from the data file creation call.

If the index file's name extension is not specified in the call to i4create() or i4open() (Index4::create() or Index4::open() in C++), CodeBase will use the standard Clipper, dBASE or FoxPro extension, depending on the compatibility format set by the programmer (see also "What are the index and data file names of Clipper, dBASE and FoxPro?").

For those using Clipper compatibility, the index file name passed to i4create() or i4open() (Index4::create() or Index4::open() in C++) is the name of the CGP file. The individual index files will still each have the .NTX file extension. To create Clipper indexes with a non-default extension, you can specify the extension name when defining the TAG4INFO.name element for any given index.

An alternate way to specify non-default Clipper extensions is to manually modify an existing CGP file and its associated index files.

For example, if the required file names are DATAFILE.ABC (instead of DATAFILE.CGP), TAG1.ABC (instead of TAG1.NTX), and TAG2.XYZ (instead of TAG2.NTX) you could perform the following steps:

1. Rename DATAFILE.CGP to DATAFILE.ABC
2. Within DATAFILE.ABC modify the names of existing indexes found in the file. For example, change the entry 'TAG.NTX' to 'TAG1.ABC', etc.
3. Rename the indexes themselves, to match the changes made to the index name entries in DATAFILE.ABC
For all cases (Clipper, dBASE and FoxPro), CodeBase will not be able to automatically open any index with a non-standard name extension. In order to do so, the CODE4.autoOpen member must be set to 0 (FALSE) before opening the file. The index must then be manually opened.

1. The CGP file has a different extension.
The CGP must be opened as in the previous example program.
2. The index (NTX) files have a different extension.
The CGP file must be edited and the name extensions should be added to the index file names. For example, suppose that an existing CGP file contains the following index files:
TAG1
TAG2
In this case, CodeBase will attempt to open TAG1.NTX and TAG2.NTX. Therefore, if the desired index files are called TAG1.ABC and TAG2.XYZ, then the CGP file must be modified as follows:
 
TAG1.ABC
TAG2.XYZ
Now when CodeBase opens the above CGP file, it will also open TAG1.ABC and TAG2.XYZ.
3. The CGP and/or index files are in separate directories.
If the CGP and index files are in different directories then the path name must be added to the CGP file. For example, the above CGP file may be modified as follows:
 
C:\DIR1\TAG1.ABC
C:\DIR2\TAG2.XYZ
When this CGP file is used in conjunction with the previous program, CodeBase will open DATAFILE.DBF in the default directory. It will then open C:\PROGRAMS\DATAFILE.ABC. Finally, CodeBase will open the index files C:\DIR1\TAG1.ABC and C:\DIR2\TAG2.XYZ.

If a CGP file is not used then t4open must be used instead. Remember that the path names must be included.

Why are all unique tags set to r4uniqueContinue, even though they were created with the r4unique option?

In the xBASE format, the only information stored to disk about a tag's uniqueness is a Boolean value that indicates whether the tag is unique or non-unique. There is no place in the tag to store more detailed information, such as whether unique tags should be handled in a fashion similar to r4unique vs. r4uniqueContinue.

In addition, the default behavior for dBASE, FoxPro and Clipper is to maintain unique tags in a manner similar to that used by CodeBase when the tag is set to r4uniqueContinue.

Consequently, in order to be compatible with their tag formats, CodeBase sets the default behavior for any unique tag to r4uniqueContinue, even if the tag was originally created with the r4unique setting. CodeBase accomplishes this be maintaining an internal structure for each tag. When the index file containing the tag is opened, CodeBase sets a specific 'unique' member of the structure to r4uniqueContinue. The possible values of this member are as follows:
 

Value	Explanation
0	Duplicate keys are allowed in the tag.
e4unique	When a duplicate key is created, via the appending of a new record or the modification of an existing record, it is not added to the tag, and an e4unique error is generated by the CodeBase function that updated/appended the record. The record is not updated.
r4unique	Same as e4unique, except no error message is generated, and the CodeBase function returns r4unique instead of e4unique.
r4uniqueContinue	When a duplicate key is created via the addition or modification of a record, the key for that record is not added to the tag, although the record containing the duplicate key is allowed to be added/updated in the data file. The CodeBase function that created the duplicate key record returns r4unique to let you know that the key was a duplicate.

 The default unique error-handling behavior for a tag is determined by the setting of the CODE4.errDefaultUnique member. If you wish to change the default setting for all tags that are opened, modify this member with one of the values listed above. The default value of this member is r4uniqueContinue.

See also: i4create (Index4::create() in C++).

My tag is indexed on the following data:

Record Number	NAME
1	AAA
2	BBB
3	BBB

The TAG4INFO settings used when the tag was created was as follows:

Name	TAG_NAME
Expression	NAME
Filter	none
Unique	r4uniqueContinue
Descending	0

In this case, the tag's uniqueness was set to 'r4uniqueContinue'. This setting tells CodeBase to allow the update or appending of a record with a duplicate key (such as record 3), but not to add an entry for that record in the index tag.

Therefore, based on the above data file, only keys for records 1 and 2 are included in the tag; there is no entry for record 3. Later, the NAME field of record 2 is changed to 'CCC'. At this point, the 'BBB' value in record 3 would no longer be a duplicate value, and you would expect all three records to appear in the index tag. But it is not. Record 3 does not have a tag entry.

Answer: For performance reasons, it is not possible for CodeBase to scan the entire data file searching for a possible record that can now be included in the index due to the modification of an existing record.

The only available work-around to this problem would be to delete the duplicate-key record, and then re-append the information to the data file, thus updating the index file tag. The best solution to this problem is not to use r4uniqueContinue on indexes where this situation might occur; instead use r4unique or e4unique.

Note also, this if you do not update the index (by removing the record and adding it back in), you will end up with a corrupted index file.

Unfortunately, there is not a simple variable stored somewhere in the database that will keep count of the number of records in an index. Although it is not difficult to create such a variable and place it in the tag, it will not be xBase compatible. It is for this reason that we have not included this functionality.

To find out the number of records in an index, just select the required index, go to the top, and skip to the bottom. Count the number of skips and add one. This number will correspond to the number of valid records in the index.

If only one numerical field is used, you only have to specify that single field in the tag expression. However, if you need to use two fields, you must convert them to strings first, and then join them in the expression. For example, if you have two numerical fields defined as:

 

Name	Type	Length	Decimals
AGE	r4num	2	0
WEIGHT	r4num	5	1

the tag expression to join the two would be:
 

"STR(AGE, 2, 0) + STR(WEIGHT, 5, 1)"
If a person is 6 years old and weighs 50.3 pounds, you would seek the text " 6 50.3".

Take note of the spaces embedded in the search string above. These spaces are required to match the search value with the size of the two fields that make up the index key expression (2 + 5).

Note also that even though this is a character tag, which is normally left justified, because the expression is based on numerical fields -- which are always right justified -- the individual sub-expressions within the tag expression are also right justified.

See also: Expression

How do I seek for a Unicode string?

In C, C++ and Delphi, pass a pointer to your Unicode string to d4seekN (Data4::seek(char*, int) in C++). Remember that the len parameter is the length ofthe string, in bytes. So if the Unicode string that you are passing is 6 Unicode characters long, len will need to be 12.

How do I seek for a value in a DateTime field?

Call d4seek or d4seekN (Data4::seek or Data4::seekN(char*, int) in C++) and pass a string in the format "CCYYMMDDhh:mm:ss:ttt" where CCYY is the year, MM is the month, DD is the day, hh is the hour, mm is the minute, ss is the second, and ttt is thousandths of the second.

For example, 2:51 pm on December 6, 1999 would be formatted as "1999120614:51:00.000".

When a record is added or modified, CodeBase will only make an update to the index. It will not rebuild the index. While this update will keep the index accurate and up to date, the layout of the index may not be as efficient as when it is reindexed.

As an example, let's say that we start with a blank database. To the database, we add these records, in this order: B, A, C, D, F, E, G. Logically, the index will look something like this:
 

This is not as efficient and compact as it could be. As each record is added to the database, CodeBase just adds the entry to the tag at the appropriate location in the tree.

When CodeBase reindexes the database, the index will logically look more like this:
 

As you can see, this version of the index contains exactly the same data as the one above, but it is organized in a much more efficient manner. Consequently, the index file consumes less disk space.

If you are using an index tag to navigate the data file, the easiest way to prevent deleted records from being encountered is to specify a filter condition when the tag is created. This can be accomplished by including the following dBASE expression in the TAG4INFO.filter member when the tag is created:
 
".NOT. DELETED()"
A second method to filter deleted records is to use the CodeBase relation functions to set up a similar filter condition. Refer to your User's Guide for more information on using relations.

Below are a few key points to help get the most out of your relate4 queries:

Let us assume the following tags have been defined:
 

Name	Expression	Filter	Unique	Descending
TAG1	FLD1	""	0	0
TAG2	FLD2	""	0	0
TAG3	FLD3	".NOT. DELETED"	0	0
TAG4	FLD4	"DELETED() .OR. .NOT. DELETED()"	0	0
TAG5	FLD5	""	0	r4descending
TAG6	FLD6+FLD7	""	0	0
TAG7	FLD7	""	r4uniqueContinue	0

• Query Optimization (QO) technology will be used only when using the relate4 queries.
• QO uses tags previously created (check the index file). That is, if the following query is made:
"(FLD1 10) .AND. (FLD2 = 'MALE') .OR. (FLD3 < 5)"
• then QO will automatically use TAG1 and TAG2 to generate the query faster.
• TAG3 will not be used because it contains a filter.
• TAG4 will not be used because it contains a filter -- note that this filter is useless since it accepts all deleted and non-deleted records. Tags with filters are not used regardless of the filter result.
• TAG5 will be used since CodeBase is indifferent to the record ordering.
• TAG6 will not be used because more than one field is included.
• TAG7 will not be used since r4uniqueContinue acts as a filter. That is, non-unique records will be in the database, but not in the index.
Activation of QO also depends on the compiler. QO uses one bit to represent each record. Therefore the following restrictions apply:
• -A 16 bit compiler is only able to allocate memory locations up to 64K bytes (2^16). Since one bit is used per record, the maximum number of records that QO can handle is 524,288. Thus, if the data file has more than half a million records then the query will be made, but QO will not be used. In this case it may be advisable to use a 32 bit compiler.
• - A 32 bit compiler is able to allocate memory locations up to 4G bytes (2^32). Since one bit is used per record, the maximum number of records that QO can handle is 34,359,738,368.

Why can QO not use a r4uniqueContinue tag?

To optimize a query, CodeBase can only use tags that have an entry for every record in the database. Since the unique type r4uniqueContinue has only one tag entry for each block of duplicate records, there may be tag entries missing for some records.

See Also: Query Optimization, r4unique, r4uniqueContinue

When the relation matches master to slave, only one slave is matched to a master at one time.

Here is an example:
 

name.dbf
ID	F_NAME	L_NAME
1	JOHN	BROWN

phone.dbf
ID	PHONE_NUM
1	444-5555
1	555-4444

internet.dbf
ID	E_MAIL
1	john@abc.com
1	jbrown@xyz.com
1	jb@isp.com

Both internet and phone are slaves of name. So name relates to phone; and name relates to internet. But internet and phone do not releate to each other.

Assuming there is no query, as you skip through the relation, the records will look like this:
 

NAME	PHONE_NUM	E_MAIL
JOHN BROWN	444-5555	<BLANK>
JOHN BROWN	555-4444	<BLANK>
JOHN BROWN	<BLANK>	john@abc.com
JOHN BROWN	<BLANK>	jbrown@xyz.com
JOHN BROWN	<BLANK>	jb@kkk.com

If you create a query such as "PHONE_NUM = '444-5555' .AND. E_MAIL = 'john@abc.com'", you would not find any records.

QO returns a bitmap which is used to indicate which records comply with a query. However, CodeBase does not have a function which will automatically count the number of records in the bit map. Consequently, a manual count must be made.

How can fields from different files be referenced in a query?

When a query is made, the default database used is the Master. This means that a specified field will automatically be associated with the master data file. For example, suppose that we are using a master data file called FATHER.DBF and a slave data file called SON.DBF. Let us also assume that each file has a field called NAME. For these data files, a query such as:
"FATHER->NAME = 'Ben Nyland'"
would compare a field called NAME in FATHER.DBF with the string "Ben Nyland". Because FATHER.DBF is the master database, an equivalent query to the above would be:
"NAME = 'Ben Nyland'"
In order to check for the composite record that has Ben Nyland and his son Eric Nyland, the query would be:
"FATHER->NAME = 'Ben Nyland' .AND. SON->NAME = 'Eric Nyland'"
As before, the following query would be equivalent to the above:
"NAME = 'Ben Nyland' .AND. SON->NAME = 'Eric Nyland'"
In conclusion, to refer to fields in different data files, use the file's (alias) name followed by the arrow ( -> ) and the field name.

Is it possible to have a master file with multiple relations to the same slave file?

Yes. In order to do so, the slave file must be opened more than once (see d4openClone). If an expression needs to explicitly refer to either the original data file or one of the clones, then aliases must be used to guarantee accurate results. For example, if the slave file's alias is "EMPLOYEE" and d4openClone() is called, CodeBase does not know which file to resolve to when the expression "EMPLOYEE->NAME = 'SMITH'" is evaluated.

This can be rectified by calling d4aliasSet() (Data4.alias() in C++) after the first instance of EMPLOYEE.DBF is opened.

See also: Alias, Query

Some expressions passed to expr4parse may be too long for CodeBase to parse properly. For instance, an expression may contain too many comparison operators. In this case, CodeBase responds with an error code of -440. In order to get around this limitation, code4calcCreate() may be used.

By using code4calcCreate, the ability to create longer expressions than would otherwise be possible is gained.

Notice that the expression MYEXPR in this example is constructed from other dBASE expressions. Furthermore, notice that when it is used, a bracket pair always follows the expression name.

In this particular example, a -440 error will be generated if the call to expr4parse is made with more than 19 comparisons. That is, if the expression "FIELD1=1 .OR. FIELD1=2 .OR. ... .OR. FIELD1=20" is passed, then the above error will be generated. Consequently, the code4calcCreate could be used for the first 19 comparisons and the query would be called as "MYEXPR() .OR. FIELD1 = 20."

See also: expr4parse, relate4querySet, Error -440

In this example, there are three fields in the table: FNAME, LNAME, CITY and COUNTRY. The query expression is "LNAME + FNAME + COUNTRY + CITY". Here is the pseudocode that will break this up:

exName = expr4parse(data,"LNAME + FNAME")
exPlace = expr4parse(data,"COUNTRY + CITY")
code4calcCreate(cb,exName,"NAME")
code4calcCreate(cb,exPlace,"PLACE")
relate4querySet(relate,"NAME() + PLACE()")

The expression is now broken down into two smaller expressions which are each made into a dBASE function. The query expression uses those functions and is shorter than what we had before.

In order to concatenate two or more field expressions together into a meaningful dBASE expression, each field expression must first be converted to a character expression. Once converted to a string each field expression may be linked to the next with the '+' operator.

Suppose that our data file includes fields that were defined as follows:
 

Name	Type	Length	Decimals
NAME	r4num	10	0
BIRTH	r4date	8	0
WEIGHT	r4num	6	2
MARRIED	r4log	1	0

In order to concatenate any of the fields together, the rules below should be applied:

• Character fields (defined as 'C' or r4str) are already in string format; thus, they do not need any conversion.
• Date fields (defined as 'D' or r4date) must be converted to strings using the 'DTOS' dBASE expression. For example, in order to convert the BIRTH field to a string, we may use the following:
DTOS(BIRTH)
• Logical fields (defined as 'L' or r4log) must be converted to strings using the 'IIF' dBASE expression. For example, in order to convert the MARRIED field to a string, we may use the following:
IIF(MARRIED, 'T', 'F')
• Numeric fields (defined as 'N' or 'F' or r4num) must be converted to strings using the 'STR' dBASE expression. For example, in order to convert the WEIGHT field to a string, we may use the following:
STR(WEIGHT, 6, 2)
Hence, to concatenate any of the above fields with another in any type of expression whether in a query or tag, convert each field to a string with the appropriate dBASE expression, and add all the individual dBASE expressions together with the '+' symbol.

In order to create an expression which uses all of the above fields, the following sequence may be used:

"NAME + STR(WEIGHT, 6, 2) + DTOS(BIRTH) + IIF(MARRIED, 'T', 'F')"

How is a query with a date field made?

In order to perform a date query, it must be ensured that a comparison is made between two identical types. That is, the date field must first be converted to a string type before making a comparison. Alternatively, the string may be converted to a date.

Suppose we have a field defined as:
 

Name	DUE_DATE
Type	r4date
Length	8
Decimals	0

To find all the records with a DUE_DATE of April 24, 2001, use one of the following queries:

relate4querySet( relation, "DTOS(DUE_DATE) = '20010424'" );
relate4querySet( relation, "DUE_DATE = STOD('20010424')" );
The above two queries yield identical results.

See also: Expression

The execution time is dependent on the time it takes to update the index file. Since you are appending many records, it will probably take less time to close the index, make the appends and then reindex.

How can I ensure optimal performance of the CodeBase database server?

• Run the server on as fast a machine as possible.
• Run the server from a local drive versus a network drive.
• Do not run any other applications on the server machine.

A good utility for finding this information is PING. On the command line, issue the following command:
PING -a xxx.xxx.xxx.xxx
Where xxx.xxx.xxx.xxx is the IP address of the machine that is to run the CodeBase server. You should get a response like this:

Pinging server5.network.com [217.53.30.5] with 32 bytes of data:



Reply from 217.53.30.5: bytes=32 time<10ms TTL=128

Reply from 217.53.30.5: bytes=32 time<10ms TTL=128

Reply from 217.53.30.5: bytes=32 time<10ms TTL=128

Reply from 217.53.30.5: bytes=32 time<10ms TTL=128

The host name in this example is "server5.network.com". That is the string to pass to the connect function.

If you do not get a host name before the IP address on the first line of the reply (server5.network.com in this example), PING cannot locate the necessary resources to resolve an IP address to a host name. See the Appendix on Protocols in your Getting Started book or contact your network administrator.

Can I speed up the time it takes to display a sorted report? I am using the Report | Sort Expression dialog box.

A sort expression is slow because it does not use the speedy Query Optimization technology (QO). You should thus try to distance yourself, whenever possible, from using this expression. Instead, use the tags that you (may have) already created. To do this you must simply choose the Relate | Modify dialog box and click the right mouse button on the master data file. Then choose the appropriate tag. Your master data file will now be sorted according to your selected tag!

How is it possible to calculate a total without showing it on the screen?

Create an area and place the 'TOTAL' object inside the new area. Since the Total will always display, you will need to suppress the area output. Therefore, set the area suppression condition to '.TRUE.'.

Another possible solution is to set the font color of the 'TOTAL' object to be identical to the background color. However, this will not work for a DOS report.

Lastly, you may create the 'TOTAL' object and set the object size to 0.

To compile LAUNCH_W.C or LAUNCH_D.C, follow the steps below:
1. Switch to the CODEREP\LAUNCH directory.
2. COPY ..\..\<LANG>\SOURCE\*.H
Where <LANG> is the 'C' or 'CPP' directory name.
3. Edit D4ALL.H and change the appropriate switches for the target application type.
4. Run the appropriate .MAK/.IDE file to compile the executable.

Your problem begins with the report design. All objects should be set to 12 points. A different size will cause too many roundoff problems.

The next step is done from the program itself. When printing reports from DOS, it is recommended that the page be reset. The following commands should be called before report4do:

• report4pageSize()
• report4margins()
• report4output()

To set the page size of the report to the physical sheet of paper, use report4pageSize() and report4margins(). Then, set the member REPORT4.screen_breaks to 1, which will display your report using the physical size of the paper instead of the screen size.

After viewing one report with an invalid printer driver, why do subsequent reports also appear blank?

Situation

The default printer is set in Windows to a printer with an invalid printer driver. CodeReporter is loaded and a report is opened. A print preview shows that the report is blank. This is correct because the printer does not exist (invalid device driver). A new printer is selected with a valid driver. The reports still display as blanks.

Answer

After selecting a legitimate printer, the report margins must be reset by the user to valid values. For instance, set all margins to one inch.

Explanation

A device driver may be invalid because the printer is not connected. Therefore, a printer device context is not allocated. Consequently, the report margins are not valid. When another (valid) printer driver is selected, CodeReporter corrects its setup of the report. However, the margins are not changed since only the user may change them.

Error Number: -1 or e4codeBase

Possible Cause

A previous CodeBase error causes CodeBase function calls to return -1.

Explanation

When a call to a CodeBase function fails, CODE4.errorCode is set to a particular error code. These codes may be found in the 'Error Codes' Appendix of the Reference Guide.  When the error code is set to a number less than 0, each subsequent CodeBase function will simply return a -1, without executing the function. This is done for safety purposes.

Solution

Set CODE4.errorCode to 0 after an error has occurred.

Error Number: -20

Description

Unable to create file

Possible Cause #1

The specified file already exists.

By default, when CodeBase attempts to create a data, index, or memo file, it does not over-write any existing file of the same name, and instead returns an error. This default behavior is specified by the value contained in the CODE4.safety member variable, which is set to 1 by default. To create a file if one by the same name already exists, set CODE4.safety to 0. See the example for CODE4.safety in the Reference Guide.

Possible Cause #2

CodeBase ran out of valid file handles.

Stand-alone 16-bit C/C++ applications

By default, only 20 file handles are available to 16-bit applications at any one time, regardless of the settings in CONFIG.SYS. Five of these handles are used by default devices such as STDOUT, STDPRN, etc. This leaves 15 file handles available for the application. Opening one data file can use up to three handles if there is also an associated index and memo file. To overcome this limitation, refer to the CodeBase COMPILER.TXT file, found in the CodeBase compiler directory for your compiler (e.g. \MSC15). If the outlined procedure is not satisfactory, contact the maker of your compiler. It is important to understand that this limitation is due to both the operating system and the compiler, not CodeBase.

Error Number: -30

Description

Determining File Length

Possible Cause

CodeBase ran out of valid file handles.

Explanation:

See Error -20.

Error Number: -440

Description

Overflow while evaluating expression

Possible Cause

The expression passed to expr4parse is too long.

Explanation:

The parsing algorithm limits the number of comparisons made in a query. Thus, very long expressions may not be parsed.

Solution

Use code4calcCreate to "shorten" the expression.

Error Number: -910

Description

Unexpected Information. Database file already open

Possible Cause

The file that is being opened has been opened previously.

Explanation

Each opened file is assigned an alias. Furthermore, no two files may share the same alias. The above error occurs when an attempt to open a file with an alias that already exists is made.

Solution

Change the file's alias with d4aliasSet, or call d4openClone() which will give a new handle to the open data file with the same alias without generated the alias error. If you need specify the data alias via a function call or through an expression, it is not defined which data handle you will get, so use with caution.

 

See also: d4aliasSet, d4openClone

Error Number: -930

Description

Unexpected Parameter

Possible Cause

A call to a CodeBase function included a parameter that was not valid.

Explanation

In some cases the programmer will forget to initialize some pointers.

Solution

Initialize the appropriate pointer.

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