The queued access method must be used to allocate an indexed sequential data set. It can also be used to sequentially process or update the data set and to add records to the end of the data set. The basic access method can be used to insert new records between records already in the data set and to update the data set directly.

Because indexed sequential data sets cannot take advantage of system-managed storage, you should consider converting indexed sequential data sets to VSAM data sets. You can use access method services to allocate a VSAM data set and copy the indexed sequential data set into it. For information about converting to VSAM data sets see Using ISAM Programs with VSAM Data Sets.