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(DSORG) An IBM term for filestructure. These include PS physical sequential, DA directaccess, IS indexed sequential, PO partitioned (alibrary). This system dates from OS/360, and breaks downbeginning with VSAM and VTAM, where it is no longerapplied.Sequential and indexed data sets can be accessed using eithera "basic" or a "queued" "access method." For example aDSORG=PS file can use either BSAM (basic sequential accessmethod) or QSAM (queued sequential access method). It canalso be processed as a direct file using BDAM. Likewise alibrary can be processed using BPAM (basic partitioned accessmethod), BSAM, QSAM, or BDAM. DSORG and access method aresomewhat, but not completely, orthogonal.The "basic" access method deals with physical blocks ratherthan records, and usually provides more control over thespecific device. Each I/O operation using the "basic"access method reads or writes a single block. A "basic" reador write starts an asynchronous I/O operation, and theprogrammer is responsible for waiting for completion andchecking for errors.The "queued" access method deals with logical records andprovides blocking and deblocking services. It is "queued"because it provides read-ahead and write-behind services.While a program is processing records in one input block, forexample, QSAM may be reading one or more blocks ahead. Queued"get" or "put" operations are synchronous as far as theprogrammer is concerned. The operation is complete when thenext logical record has been successfully processed.EXCP (Execute Channel Program) is a lower-level method ofaccessing data.IBM manuals usually named "Data Administration Guide",e.g. SC26-4505-1 for MVS/ESA DFP 3.1, provide more detailabout data set organizations and access methods.