z/OS V1R6.0 DFSMS Access Method Services for Catalogs

DEFINE CLUSTERProgramming: Authorized Assembler Services Reference ALE-DYNand z/OS MVS Programming: Authorized Assembler ServicesReference LLA-SDU.)4 Indicates that the data set can be fully shared. For each request,VSAM refreshes the buffers used for direct processing. Thisoption requires that you use the RESERVE and DEQ macros tomaintain data integrity while sharing the data set. Improperuse of the RESERVE macro can cause problems similar to thosedescribed under SHAREOPTIONS 3. (For information on usingRESERVE and DEQ, see z/OS MVS Programming: AuthorizedAssembler Services Reference ALE-DYN and z/OS MVSProgramming: Authorized Assembler Services Reference LLA-SDU.)Output processing is limited to update, or add processing, orboth that does not change either the high-used RBA or theRBA of the high key data control interval if DISP=SHR isspecified.To ensure data integrity in a shared environment, VSAM provides users ofSHAREOPTIONS 4 (cross-region and cross-system) with the followingassistance:vvEach PUT request immediately writes the appropriate buffer to the VSAMcluster’s DASD space. That is, the buffer in the user’s address space thatcontains the new or updated data record, and the buffers that contain newor updated index records when the user’s data is key-sequenced.Each GET request refreshes all the user’s input buffers. The contents of eachdata and index buffer being used by the user’s program is retrieved from theVSAM cluster’s DASD.Abbreviation: SHRSPANNED|NONSPANNEDSpecifies whether a data record is allowed to cross control interval boundaries.If SPANNED or NONSPANNED is specified in the SMS data class, the valuedefined is used as the data set definition, unless it has been previously definedwith an explicitly specified or modeled DEFINE attribute.This parameter cannot be used when defining a linear data set cluster.SPANNEDSpecifies that, if the maximum length of a data record (as specified withRECORDSIZE) is larger than a control interval, the record is contained onmore than one control interval. This allows VSAM to select a controlinterval size that is optimum for the DASD.When a data record that is larger than a control interval is put into acluster that allows spanned records, the first part of the record completelyfills a control interval. Subsequent control intervals are filled until therecord is written into the cluster. Unused space in the record’s last controlinterval is not available to contain other data records.Using this parameter for a variable-length relative record data set causesan error.Abbreviation: SPNDNONSPANNEDIndicates that the record must be contained in one control interval. VSAMselects a control interval size that accommodates your largest record.164 z/OS V1R6.0 DFSMS Access Method Services for Catalogs