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Of course, when making a structure UNALIGNED is not possible, there is a way of making the black hole slightly less black, by following the advice given at the end of Chapter 13, "Improving performance" of the "Enterprise PL/I for z/OS Programming Guide": <div>&nbsp;</div> "When your code refers to a member of a BASED structure using REFER, the compiler often has to generate one or more calls to a library routine to map the structure at run-time. These calls can be expensive, and so when the compiler makes these calls, it will issue a message so that you can locate these potential hot-spots in your code. <div>&nbsp;</div> If you do have code that uses BASED structures with REFER and which the compiler flags with this message, you may be able to get better performance by passing the structure to a subroutine that declares a corresponding structure with * extents. This will cause the structure to be mapped once at the CALL statement, but there will no further remappings when it is accessed in the called subroutine."