Using an alternate collating sequence means modifying the collating sequence for character match fields (file selection) and character comparisons. You specify that an alternate collating sequence will be used by specifying the ALTSEQ keyword on the control specification. The calculation operations affected by the alternate collating sequence are ANDxx, COMP, CABxx, CASxx, DOU, DOUxx, DOW, DOWxx, IF, IFxx, ORxx, WHEN, and WHENxx. This does not apply to graphic or UCS-2 compare operations. LOOKUP and SORTA are affected only if you specify ALTSEQ(*EXT). The characters are not permanently changed by the alternate collating sequence, but are temporarily altered until the matching field or character compare operation is completed.
Use the ALTSEQ(*NONE) keyword on the definition specification for a variable to indicate that when the variable is being compared with other character data, the normal collating sequence should always be used even if an alternate collating sequence was defined.
Changing the collating sequence does not affect the LOOKUP and SORTA operations (unless you specify ALTSEQ(*EXT)) or the hexadecimal values assigned to the figurative constants *HIVAL and *LOVAL. However, changing the collating sequence can affect the order of the values of *HIVAL and *LOVAL in the collating sequence. Therefore, if you specify an alternate collating sequence in your program and thereby cause a change in the order of the values of *HIVAL and *LOVAL, undesirable results may occur.