Insertions into a key-sequenced data set use the free space provided during the definition of the data set or the free space that develops because of control interval and control area splits. To create a data set or make mass insertions, use RPL OPTCD=SEQ,NUP or NSP. RPL OPTCD=SEQ,NUP or NSP inserts the records sequentially and maintains free space during load mode and during mass insertions. All the other types use the direct insert strategy. If MACRF=SIS is specified in the ACB, all inserts use sequential insert strategy.

With addressed access of a key-sequenced data set, VSAM does not insert or add new records.

Sequential Insertion. If the new record belongs after the last record of the control interval and the record contains free space, the new record is inserted into the existing control interval. If the control interval does not contain sufficient free space, the new record is inserted into a new control interval without a true split.

If the new record does not belong at the end of the control interval and there is free space in the control interval, it is placed in sequence into the existing control interval. If adequate free space does not exist in the control interval, a control interval split occurs at the point of insertion. The new record is inserted into the original control interval and the following records are inserted into a new control interval.

Mass Sequential Insertion. When VSAM detects two or more records to be inserted in sequence into a collating position (between two records) in a data set, VSAM uses a technique called mass sequential insertion to buffer the records being inserted, and to reduce I/O operations. Using sequential instead of direct access takes advantage of this technique. Also extend your data set (resume loading) by using sequential insertion to add records beyond the highest key or relative record number. There are possible restrictions to extending a data set into a new control area depending on the specified share options. See Sharing VSAM Data Sets.

Mass sequential insertion observes control interval and control area free space specifications when the new records are a logical extension of the control interval or control area (that is, when the new records are added beyond the highest key or relative record number used in the control interval or control area).

When several groups of records in sequence are to be mass inserted, each group can be preceded by a POINT with RPL OPTCD=KGE to establish positioning. KGE specifies that the key you provide for a search argument must be equal to the key or relative record number of a record.

Direct Insertion—CI Split. If the control interval has enough available space, the record is inserted. If the control interval does not have enough space to hold the record, the entire CI is split, unless the record is the last key in the file. The last record is always placed in a new, empty CI and does not show up as a CI split.

Direct Insertion—CA Split. If no additional CI is available to allow a CI split, the CA is split. For the last record in the file, however, the new record is inserted as the first record in a new, empty CA. This does not show up as a CA split. If the new record belongs after the last record of the control interval and there is still space, the new record is added to the end of the existing control interval. If the control interval does not contain sufficient free space, the new record is inserted into an unused control interval.