This section covers the following topics:
The SQL support of Natural combines the flexibility of dynamic SQL support with the high performance of static SQL support.
In contrast to static SQL support, Natural dynamic SQL support does not require any special considerations with regard to the operation of the SQL interface. All SQL statements required to execute an application request are generated automatically and can be executed immediately with the Natural system command RUN. Before executing a program, you can look at the generated SQL code, using the LISTSQL command.
Access to SQL/DS through Natural has the same form whether dynamic or static SQL support is used. Thus, with static SQL support, the same SQL statements in a Natural program can be executed in either dynamic or static mode. An SQL statement can be coded within a Natural program and, for testing purposes, it can be executed using dynamic SQL. If the test is successful, the SQL statement remains unchanged and static SQL for this program can be generated.
Thus, during application development, the programmer works in dynamic mode and all SQL statements are executed dynamically, whereas static SQL is only created for applications that have been transferred to production status.
Natural automatically provides for the preparation and execution of each SQL statement and handles the opening and closing of cursors used for scanning a table.
This section covers the following topics:
As each dynamic execution of an SQL statement requires a statically defined DECLARE STATEMENT and DECLARE CURSOR statement, a special I/O module (NDBIOMO) is provided which contains a fixed number of these STATEMENTs and CURSORs. This number is specified during the generation of NDBIOMO.
If possible, an SQL statement is only prepared once and can then be executed several times if required. For this purpose, Natural internally maintains a table of all SQL statements that have been prepared and assigns each of these statements to a DECLAREd STATEMENT in NDBIOMO. In addition, this table maintains the cursors used by the SQL statements SELECT, FETCH, UPDATE (Positioned), and DELETE (Positioned).
Each SQL statement is uniquely identified by:
the name of the Natural program that contains this SQL statement,
the line number of the SQL statement in this program,
the name of the Natural library into which this program was stowed,
the time stamp when this program was stowed.
Once a statement has been prepared, it can be executed several times with different variable values, using the dynamic SQL statement EXECUTE USING DESCRIPTOR or OPEN CURSOR USING DESCRIPTOR respectively.
When the full capacity of the statement table is reached, the entry for the next prepared statement overwrites the entry for a free statement whose latest execution is the least recent one.
When a new SELECT statement is requested, a free entry in the statement table with the corresponding cursor is assigned to it and all subsequent FETCH, UPDATE, and DELETE statements referring to this SELECT statement will use this cursor. Upon completion of the sequential scanning of the table, the cursor is released and free for another assignment. While the cursor is open, the entry in the statement table is marked as used and cannot be reused by another statement.
If the number of nested FIND (SELECT) statements reaches the number of entries available in the statement table, any further SQL statement is rejected at execution time and a Natural error message is returned.
The size of the statement table depends on the size specified for NDBIOMO. Since the statement table is contained in the SQL/DS buffer area, the DB2SIZE parameter may not be sufficient and may need to be increased.
The embedded SQL uses cursor logic to handle SELECT statements. The preparation and execution of a SELECT statement is done as follows:
The typical SELECT statement is prepared by a program flow which contains the following embedded SQL statements (note that X and SQLOBJ are SQL variables, not program labels, and that the question marks below are parameter markers which indicate where values are to be inserted at execution time.):
DECLARE SQLOBJ STATEMENT DECLARE X CURSOR FOR SQLOBJ INCLUDE SQLDA (copy SQL control block)
Then, the following statement is moved into SQLSOURCE:
SELECT PERSONNEL_ID, NAME, AGE FROM EMPLOYEES WHERE NAME IN (?, ?) AND AGE BETWEEN ? AND ? PREPARE SQLOBJ FROM SQLSOURCE
Then, the SELECT statement is executed as follows:
OPEN X USING DESCRIPTOR SQLDA FETCH X USING DESCRIPTOR SQLDA
The descriptor SQLDA is used to indicate a variable list of program areas. When the OPEN statement is executed, it contains the address, length and type of each value which replaces a parameter marker in the WHERE clause of the SELECT statement. When the FETCH statement is executed, it contains the address, length and type of all program areas which receive fields read from the table. When the FETCH statement is executed for the first time, it sets the Natural system variable *NUMBER to a non-zero value if at least one record is found that meets the search criteria. Then, all records satisfying the search criteria are read by repeated execution of the FETCH statement.
Once all records have been read, the cursor is released by executing the following statement:
CLOSE X
Static SQL is generated in Natural batch mode for one or more Natural applications which can consist of one or more Natural object programs. The number of programs that can be modified for static execution in one run of the generation procedure is limited to 999.
During the generation procedure, the database access statements contained in the specified Natural objects are extracted, written to work files and transformed into a temporary Assembler program. If no Natural program is found that contains an SQL access or if any error occurs during static SQL generation, batch Natural terminates and condition code 40 is returned, which means that all further JCL steps should no longer be executed.
The temporary Assembler program is written to a temporary file (the Natural work file CMWKF06) and precompiled. During precompilation, a static SQL/DS package (access module) is created and after the precompilation, the precompiler output is extracted from the Assembler program and written to the corresponding Natural objects, which means that the Natural objects are modified (prepared) for static execution. The temporary Assembler program is no longer used and deleted.
Note:
Since the Assembler precompiler of SQL/DS does not support GRAPHIC
field types, you cannot generate a static Assembler program if your Natural
program(s) contain any references to GRAPHIC-type columns.
The Natural subprogram NDBDBRM can be used to check whether a Natural program contains an SQL access and whether it has been modified for static execution.
This section covers the following topics:
Under z/VSE, a static SQL/DS package is created by using the sample job I075.
The job I075 consists of the following steps:
Define six Natural work files for output.
Define as PHASE search library the library that contains the Natural batch module and the library where you installed this Natural for SQL/DS version (since the static generation process uses the Natural modules NDBSTAT and NDBCHNK).
Define the necessary Natural commands and the Natural input for the static generation procedure.
The output (CMWKF06) consists of a temporary Assembler program which contains all the database access statements of the Natural objects involved and serves as input for the precompilation step below.
Define as PHASE search library the library where you installed SQL/DS.
Define the necessary precompiler options and specify your SQL user ID and password.
The precompiler output consists of a static SQL/DS package and a precompiled temporary Assembler program (IJSYSPH) which contains all the database access statements transformed from SQL into Assembler statements and serves as input for the modification step below.
Define as PHASE search library the library that contains the Natural batch module.
Define the necessary Natural commands and the Natural input for the object modification procedure.
The output consists of a modified Natural object which contains all required SQL/DS access information.
To generate static SQL for Natural programs, LOGON to library SYSSQL.
Note:
Since a new SYSSQL library has been created when installing Natural
for SQL/DS, ensure that it contains all Predict interface programs necessary to
run the static SQL generation. These programs are loaded into SYSSQL during
Predict installation (see the relevant Predict documentation).
Then specify the CMD CREATE command and the Natural input necessary for the static SQL generation process; the CMD CREATE command has the following syntax:
CMD
CREATE DBRM
static-name
USING
using-clause |
{
application-name,object-name,excluded-object
} |
:
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:
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The generation procedure reads but does not modify the specified Natural objects. If one of the specified programs was not found or had no SQL access, return code 4 is returned at the end of the generation step.
If the PREDICT DOCUMENTATION option is to be used, a corresponding Predict static SQL entry must be available and the static-name must correspond to the name of this entry. In addition, the static-name must correspond to the name of the static SQL/DS package to be created during precompilation. The static-name can be up to 8 characters long and must conform to Assembler naming conventions.
The using-clause specifies the Natural objects to be contained in the static SQL/DS package. These objects can either be specified explicitly as INPUT DATA in the JCL or obtained as PREDICT DOCUMENTATION from Predict.
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WITH XREF
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[LIB
lib-name] |
If the parameters to be specified do not fit in one line, specify the command identifier (CMD) and the various parameters in separate lines and use both the input delimiter (as specified with the ID parameter; default is ",") and the continuation indicator (as specified with the CF parameter; default is "%") as shown in the example below.
CMD CREATE,DBRM,static,USING,PREDICT,DOCUMENTATION,WITH,XREF,NO,% LIB,library
Alternatively, you can also use abbreviations as shown in the following example:
CMD CRE DBRM static US IN DA W XR Y LIB library
The sequence of the parameters USING, WITH and LIB is optional.
As input data, the applications and names of the Natural objects to be included in the static SQL/DS package must be specified in the subsequent lines of the job stream (application-name,object-name). A subset of these objects can also be excluded again (excluded-objects). Objects in libraries whose name begins with "SYS" can be used for static generation, too.
The applications and names of Natural objects must be separated by the input delimiter (as specified with the ID parameter; default is ","). If you wish to specify all objects whose name begins with a specific string of characters, use an object-name or excluded-objects name that ends with asterisk notation (*). To specify all objects in an application, use asterisk notation only.
LIB1,ABC* LIB2,A*,AB* LIB2,* ...
The specification of applications/objects must be terminated by a line that contains a period (.) only.
As Predict supports static SQL for SQL/DS, you can also have Predict supply the input data for creating static SQL by using already existing PREDICT DOCUMENTATION.
As Predict Active References supports static SQL for SQL/DS, the generated static SQL/DS package can be documented in Predict and the documentation can be used and updated with Natural.
WITH XREF is the option which enables you to store cross-reference data for a static SQL entry in Predict each time a static SQL/DS package is created (YES). You can instead specify that no cross-reference data are stored (NO) or that a check is made to determine whether a Predict static SQL entry for this static SQL/DS package already exists (FORCE). If so, cross-reference data are stored; if not, the creation of the static SQL/DS package is not allowed. For more information on Predict Active References, refer to the Predict documentation.
When WITH XREF (YES/FORCE) is specified, XREF data are written for both the Predict static SQL entry (if defined in Predict) and each generated static Natural program. However, static generation with WITH XREF (YES/FORCE) is possible only if the corresponding Natural programs have been cataloged with XREF ON.
WITH XREF FORCE only applies to the USING INPUT DATA option.
Note:
If you do not use Predict, the XREF option must be omitted or set
to NO and the module NATXRF2 need not be linked to the Natural nucleus.
With the LIB option, a Predict library other than the default library (*SYSSTA*) can be specified to contain the Predict static SQL entry and XREF data. The name of the library can be up to eight characters long.
The modification procedure modifies the Natural objects involved by writing precompiler information into the object and by marking the object header with the static-name as specified with the CMD CREATE command.
In addition, any existing copies of these objects in the Natural global buffer pool (if available) are deleted and XREF data are written to Predict (if specified during the generation procedure).
To perform the modification procedure, LOGON to SYSSQL and specify the CMD MODIFY command which has the following syntax:
CMD
MODIFY [ XREF ]
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The input for the modify step is the precompiler output which must reside on a dataset defined as the Natural work file CMWKF01.
The output consists of precompiler information which is written to the corresponding Natural objects. In addition, a message is returned telling you whether it was the first time an object was modified for static execution ("modified") or whether it had been modified before ("re-modified").
If the XREF option is specified, the Natural work file CMWKF02 must be defined to contain the resulting list of cross-reference information concerning the statically generated SQL statements (see also Assembler/Natural Cross-References).
If you specify the XREF option of the MODIFY command, an output listing is created on the work file CMWKF02, which contains the static SQL/DS package name and the Assembler statement number of each statically generated SQL statement together with the corresponding Natural source-code line number, program name, library name, database ID and file number.
------------------------------------------------------------------------
DBRMNAME STMTNO LINE NATPROG NATLIB DB FNR COMMENT
------------------------------------------------------------------------
DEM2S 000087 0170 DEM2SUPD HGK 00010 00032 SELECT
000111 0230 UPD/DEL
DEM2S 000121 0370 DEM2SINS HGK 00010 00032 INSERT
DEM2S 000131 0150 DEM2SDEL HGK 00010 00032 SELECT
000155 0170 UPD/DEL
DEM2S 000165 0040 DEM2SDL2 HGK 00010 00032 UPD/DEL
| Column | Explanation |
|---|---|
| DBRMNAME | Name of the static SQL/DS package which contains the static SQL statement. |
| STMTNO | Assembler statement number of the static SQL statement. |
| LINE | Corresponding Natural source code line number. |
| NATPROG | Name of the Natural program that contains the static SQL statement. |
| NATLIB | Name of the Natural library that contains the Natural program. |
| DB / FNR | Natural database ID and file number. |
| COMMENT | Type of SQL statement. |
To be able to execute Natural in static mode, all users of Natural must have the SQL/DS RUN privilege for the static SQL/DS package created at precompilation.
To execute static SQL start Natural and execute the corresponding Natural program. Internally, the Natural runtime interface evaluates the precompiler data written to the Natural object and then performs the static accesses.
To the user there is no difference between dynamic and static execution.
Static generation can be disallowed with Natural Security by:
restricting access to library SYSSQL,
disallowing the module CMD,
restricting access to the libraries that contain the relevant Natural objects,
disallowing one of the commands CATALOG or STOW for a library that contains relevant Natural objects.
If a library is defined in Natural Security and the DBID and FNR of this library are different from the default specifications, the static generation procedure automatically switches to the DBID and FNR specifications defined in Natural Security.
It is possible to operate Natural in a mixed static and dynamic mode where static SQL is generated for some programs.
The mode in which a program is run is determined by the Natural object program itself. If a static SQL/DS package is referenced in the executing program, all statements in this program are executed in static mode.
Note:
Natural programs which return a runtime error do not automatically
execute in dynamic mode. Instead, either the error must be corrected or, as a
temporary solution, the Natural program must be recataloged to be able to
execute in dynamic mode.
Within the same Natural session, static and dynamic programs can be mixed without any further specifications. The decision which mode to use is made by each individual Natural program.
This section lists the error messages that may be issued during static generation.
Program NDBCHNK has been invoked to allocate space for Natural object load, but the allocation has failed; retry or increase the free storage pool.
Program NDBCHNK has been invoked to write a Natural object row into the appropriate buffer, but the write has failed; this is probably a NDBCHNK program error.
Program NDBSTAT has been invoked to retrieve next SQL/DS statement information from the Natural object loaded in main storage, but the retrieval has failed (RC was neither 0 (OK) nor 4 (EOP)); the probable cause is a Natural object inconsistency.
Program NDBSTAT has been invoked to retrieve next SQL/DS statement information from the Natural object loaded in main storage, but the Adabas command code returned was invalid; the probable cause is a Natural object inconsistency.
Program NDBCHNK has been invoked to free the area allocated for Natural object load, but the release has failed; this is probably a program error.
Program NDBSTAT has been invoked to know the time stamp associated to the loaded Natural object, but the call has failed; this is probably a program error.
Program NDBSTAT has been invoked to retrieve the next compilation A-list element, but the retrieval has failed (RC was neither 0 (OK) nor 20 (EOL)); the probable cause is a Natural object inconsistency.
Program NDBSTAT has been invoked to retrieve the next compilation A-list element, but the SQL/DS format code returned is invalid; the probable cause is a Natural object inconsistency.
The SQL/DS precompiler parameter (mailbox length) does not fit into a halfword, which means that the SQL statement contains too many variables.
The table for a second selection logs the statement number of all second SELECT statements. The table is reset if there are more than 100 entries, which means with many nested program loops. If the table is reset, no second UPDATE or DELETE statements are generated.
The versions of the Natural programs used for the static generation (library SYSSQL) must be the same as one of the dynamically loaded Assembler program NDBSTAT.
Expl.: A Natural object address was not found and the object cannot be modified. Either the object was not found or the address was wrong.
Natural terminates abnormally with RC=4. A Natural member was explicitly entered which does not exist or does not have SQL access. The static generation can continue.
The temporary assembler program for the precompiler input was written to a temporary dataset (Natural work file 5).
None of the programs processed by the CMD command accessed an SQL system.
The module name specified with the CMD CREATE command must be the same as the name of the DBRM specified in the DBRMLIB job card of the precompilation step.
The number of programs to be generated statically into one DBRM exceeds the maximum of 999.
The maximum number of 1500 NULL indicators per SQL statement has been exceeded.
The number of variables to be generated statically for one program exceeds the maximum of 9999.
The Predict DDA default setting for static SQL XREF is set to "YES", but the XREF option in the CMD command is set to "NO".
With the XREF option FORCE, the static generation continues and writes XREF data only if Predict documentation exists for a given DBRM. If there is no Predict documentation available, static generation is not performed.
Either the Natural program which is to be statically generated cannot be cataloged with XREF=ON or the XREF data are not on the used Predict file.
The Predict DDA default setting for static SQL XREF is set to "FORCE", but the XREF option in the CMD command is set to "NO" or "YES".
The library for the DBRM entered with the LIB option is not defined as 3GL application in Predict. Check the library name in Predict which contains the DBRM.
The commands CATALOG or STOW are not allowed in your security environment. However, the CATALOG or STOW privilege is needed for static generation.
No documentation was found in Predict for the DBRM specified with the CMD command. Either the DBRM is not documented in the used Predict file or a wrong DBRM name has been specified.
The Predict DDA default setting for static SQL XREF is read, because no XREF option is specified in the CMD command and the XREF interface and Predict are installed.
The program was recataloged during the static generation process. The modify step did not change the program object. Static generation modify step continues with the next program.