VSAM： Virtual storage access method 虚拟存储访问方法是IBM的磁盘文档存储访问方法， 首先使用在0S/VS2操作系统中，然后使用在多虚拟存储架构，现在在z/OS。 作为一个面向记录的文档系统，VSAM由四个数据集组成。关键字顺序数据集KSDS, 关联记录数据集RRDS， 实体顺序数据集ESDS和线性数据集LDS。 KSDS,RRDS和ESDS由记录组成， 而LDS只包含无固定记录结构的字节流。

Virtual storage access method (VSAM) is an IBM DASD file storage access method, first used in the OS/VS1, OS/VS2 Release 1 (SVS) and Release 2 (MVS) operating systems, later used throughout the Multiple Virtual Storage (MVS) architecture and now in z/OS. Originally a record-oriented filesystem., VSAM comprises four data set organizations: Key Sequenced Data Set (KSDS), Relative Record Data Set (RRDS), Entry Sequenced Data Set (ESDS) and Linear Data Set (LDS). The KSDS, RRDS and ESDS organizations contain records, while the LDS organization (added later to VSAM) simply contains a sequence of pages with no intrinsic record structure, for use as a memory-mapped file.