IBM OS Linkage Editor and Loader GC28-6538

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To assign the serially reusable attribute, code REUS in the PARM field, as follows: //LKED EXEC PGM=IEWL,PARM=·REUS, ••• • Refreshable Attribute A module with the refreshable attribute can be replaced by a new copy during execution by a recovery management routine without changing either the sequence or results of processing. This type of module cannot be modified by itself or by any other module during execution. The linkage editor only stores the attribute in the directory entry; it does not check whether the module is refreshable. If a module is to be refreshable, all of the control sections within it must be refreshable. If the refreshable attribute is specified, and any load modules that are not refreshable become a part of the input to the linkage editor, the attribute is negated. To assign the refreshable attribute, code REFR in the PARM field, as follows: //LKED EXEC PGM=IEWL,PARM=·REFR, ••• • Scatter Format Attribute A module with the scatter format attribute need not be loaded into a contiguous block of main storage: rather, the programmer can specify the dynamic loading of control sections into noncontiguous, or scattered, areas within his assigned main storage area. Although scatter loading can also be left to the control program, the programmer should specify the loading process himself for most effective use of available storage. If the scatter format attribute is not specified, the linkage editor produces a load module in a format suitable for block loading. That is, the control program can load the module only into one contiguous main storage area large enough to contain the complete module. When the scatter format attribute is specified, the linkage editor produces a load module in a format suitable for either scatter or block loading. If the scatter load feature is not available in the control program, modules with the scatter format attribute are block loaded. To assign the scatter format attribute, code SCTR in the PARM field, as follows: //LKED EXEC PGM=IEWL,PARM='SCTR, ••• • Note 1: The block format attribute is assigned by the linkage editor if scatter format is not specified. (The programmer cannot specify block format.) Note 2: SCTR is specified, the programmer should ensure that the load module does not contain zero-length control sections, private code sections, or common areas. The presence of such sections in a module that is to be scatter loaded can, under certain circumstances, cause Program Fetch to terminate abnormally when the module is loaded into main storage for execution. 94
Test Attribute A module with the test attribute is to be tested and contains the testing symbol tables for the test translator (TESTRAN) or the TSO TEST command. The linkage editor accepts these tables as input, and places them in the output module. The module is marked as being under test. If the test attribute is not specified, the symbol tables are ignored by the linkage editor and are not placed in the output module. If the test attribute is specified, and no symbol table input is received, the output load module will not contain symbol tables to be used by TESTRAN or the TSO TEST command. To assign the test attribute, code TEST in the PARM field, as follows: //LKED EXEC PGM=IEWL,PARM='TEST, ••• • Note 1: The test attribute applies primarily to assembler language programs using TESTRAN or the TSO TEST command. Note 2: Modules that use TESTRAN should not be marked with the RENT, REUS, or REFR attribute. Default Attributes Unless specific module attributes are indicated by the programmer, the output module is not in an overlay structure, and it is not tested (assembler only). The module is in block format, not refreshable, not re-enterable, not serially reusable, and cannot be reprocessed by the level E linkage editor. One other attribute is specified by the linkage editor after processing is finished. If, during processing, severity 2 errors were found that would prevent the output module from being executed successfully, the linkage editor assigns the not executable attribute. The control program will not load a module with this attribute. If the LET option is specified, the output module is marked executable even if severity 2 errors occur. The LET option is discussed later in this section. Incompatible Attributes Although there are ten module attributes that the programmer may specify, several are mutally exclusive. When mutually exclusive attributes are specified for a load module, the linkage editor ignores the less Significant attributes. For example, if both OVLY and RENT are specified, the module will be in an overlay structure and will not be re-enterable. Certain attributes are also incompatible with other job step options. For convenience, all job step options are shown in Figure 34 at the end of this chapter along with those options that are incompatible. Job Control Language Summary 95
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Systems Reference Library IBM OS Li
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INTRODUCTION • • • • • 9
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INTRODUCTION The linkage editor and
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Figure 5. Input, Intermediate, and
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FUNCTIONS OF THE LINKAGE EDITOR Lin
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Figure 8. Linkage Editor Processing
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defines a control section named MAI
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In the next example, the primary in
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Additional Call Libraries If additi
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INCLUDED DATA SETS The INCLUDE cont
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Library Members: Members from more
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SAMPLE PROGRAM RPLACJOB Sample prog
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IBM Confidential The job control la
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VL The sequence of the a-byte entri
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• Make sure that MSGLEVEL=(l,l) w
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Figure 46. Loader Processing -- SYS
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MAP The loader options are: NOMAP A
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Sharing Option (TSO) of the operati
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-----------------------------------
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Figure 58 shows the compilation and
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• For each load module containing
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COBOL language dependencies 25 coll
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input to linkage editor 28-31 with
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READER'S COMMENTS TITLE: IBM OS Lin
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IBM OS Linkage Editor and Loader GC28-6538

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