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Specifying SHAREOPTIONS=4 (SHAREOPTIONS=(n,4) or SHAREOPTIONS=(4,n)) informs VSAM that the file is being used by multiple systems. This forces a physical READ or WRITE every time a record is accessed, so no benefit is achieved by using LSR or extra buffers. VSAM fails the OPEN if SHAREOPTIONS=4 and LSR are both specified. So, if VPE encounters this option, it excludes this file in the buffer pool and issues a warning. Do not use SHAREOPTIONS=4 unless you need it.
Note: If a cluster has SHAREOPTIONS=(n,4) specified, any of its alternate indexes that were created with the option of UPGRADE are assumed to be SHAREOPTIONS=(n,4) even if they were not defined that way. The same is true for a cluster that is not SHAREOPTIONS=(n,4), if any one of its upgrade AIXs were created with SHAREOPTIONS=(n,4).
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