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

ALTERSMS-managed volumes, and catalogs containing SMS-managed data sets, mustnot be shared with non-SMS systems. (For a description of data set sharing, seez/OS DFSMS: Using Data Sets).The value of SHAREOPTIONS is assumed to be (3,3) when the data set isaccessed in VSAM RLS or DFSMStvs mode.crossregionSpecifies the amount of sharing allowed among regions within the samesystem or within multiple systems using global resource serialization(GRS). Independent job steps in an operating system, or multiple systemsin a GRS ring, can access a VSAM data set concurrently. For a descriptionof GRS, see z/OS MVS Planning: Global Resource Serialization. Option 3 is theonly one applicable for altering a catalog. To share a data set, each usermust code DISP=SHR in the data set’s DD statement. You can use thefollowing options:OPT 1 The data set can be shared by any number of users for readprocessing, or the data set can be accessed by only one user forread and write processing. VSAM ensures complete data integrityfor the data set. This setting does not allow any non-RLS accesswhen the data set is already open for VSAM RLS or DFSMStvsprocessing. A VSAM RLS or DFSMStvs open will fail with thisoption if the data set is already open for any processing.OPT 2 The data set can be accessed by any number of users for readprocessing, and it can also be accessed by one user for writeprocessing. It is the user’s responsibility to provide read integrity.VSAM ensures write integrity by obtaining exclusive control for acontrol interval while it is being updated. A VSAM RLS orDFSMStvs open is not allowed while the data set is open fornon-RLS output.If the data set has already been opened for VSAM RLS orDFSMStvs processing, a non-RLS open for input is allowed; anon-RLS open for output fails. If the data set is opened for input innon-RLS mode, a VSAM RLS or DFSMStvs open is allowed.OPT 3 The data set can be fully shared by any number of users. The useris responsible for maintaining both read and write integrity for thedata the program accesses. This setting does not allow anynon-RLS access when the data set is already open for VSAM RLSor DFSMStvs processing. If the data set is opened for input innon-RLS mode, a VSAM RLS or DFSMStvs open is allowed.This option is the only one applicable to a catalog.OPT 4 The data set can be fully shared by any number of users. For eachrequest, VSAM refreshes the buffers used for direct processing.This setting does not allow any non-RLS access when the data setis already open for RLS or DFSMStvs processing. If the data set isopened for input in non-RLS mode, a VSAM RLS or DFSMStvsopen is allowed.As in SHAREOPTIONS 3, each user is responsible for maintainingboth read and write integrity for the data the program accesses.crosssystemIs the amount of sharing allowed among systems. Job steps of two or moreoperating systems can gain access to the same VSAM data set regardless ofthe disposition specified in each step’s DD statement for the data set. ToChapter 5. ALTER 69