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Use FOCUS with the VSAM Write Data Adapter to create new VSAM data sources as well as updating existing ones. When creating a new one you must first calculate and allocate disk space for it following standard VSAM procedures before you initially load it. Use the DEFINE function of the IBM IDCAMS utility program to create it, as the FOCUS CREATE command, which is used to create FOCUS data sources and erase data in them, does not work with VSAM. All FOCUS MODIFY and MAINTAIN features can be used with the VSAM Write Data Adapter. These topics identify particular aspects of the MATCH, NEXT, LOOKUP, COMBINE, FIND, REPOSITION, and REPEAT functions unique to VSAM. |
Topics: Simultaneous Usage (SU) Mode for VSAM Data Sources in MVS Modifying Records: The MATCH and NEXT Statements in VSAM Accessing Fields in Joined Data Structures With LOOKUP in VSAM Modifying Multiple Data Sources: The COMBINE Facility in VSAM |
Controlling the Current Record Position With REPOSITION in VSAM Looping Through Files With REPEAT in VSAM Modifying Variable-Length OCCURS Segments in VSAM |
MATCH and NEXT processing are also discussed herein. MATCH processing can only be performed on full key fields, on parts of the key fields, or on non-key fields. Unlike standard FOCUS processing of SO segment types, however, VSAM does not allow inclusion of new records with duplicate keys within key-sequenced data sets.
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