Dataset Types Comparison
Dataset Types Comparison
VSAM supporting access modes and record length -
| File Organization | Access Type | Record Length | |||
|---|---|---|---|---|---|
| Sequential Access | Random Access | Dynamic Access | Fixed-length | Variable-length | |
| ESDS | Yes | No | No | Yes | Yes |
| KSDS | Yes | Yes | Yes | Yes | Yes |
| RRDS | Yes | Yes | Yes | Yes | Yes |
ESDS, KSDS, RRDS, VRRDS, and LDS Comparison -
| ESDS | KSDS | Fixed-length RRDS | Variable-length RRDS | LDS | |
|---|---|---|---|---|---|
| What is the method for sequential access? | Entry/Inserting order | Primary key ascending order | RRN order | RRN order | No record level processing |
| What are the types of record format? | Fixed-length Variable-length Spanned records |
Fixed-length Variable-length Spanned records |
Fixed-length | Variable-length | No record level processing |
| What is the method for direct access? | RBA | Key or RBA | RRN | RRN | Acess with DIV (Data-In-Virtual) |
| What are the Components the dataset have? | DATA Component | DATA and INDEX Components |
DATA Component | DATA and INDEX Components |
DATA Component |
| Can RBA or RRN change? | A records's RBA can't change | A records's RBA can change | A records's RRN can't change | A records's RRN can't change | No record level processing |
| Can we delete the record? | Record can't be deleted. We can reuse the record for a record of the same length. | Deleting the record space becomes free space. | Slot freeed by deleting the record can be reused. | Deleting the record space becomes free space. | No record level processing |
| Can we reuse the deleted record space? | No | Yes | Yes | Yes | No record level processing |
| Is record length changeable? | No | Yes | No | Yes | Extended format allowed |
| Where are new records added? | End of the file | Anywhere | RRN Slot | RRN Slot | CI |
| Can you REUSE the file? | Yes (If no AIX) | Yes (If no AIX) | Yes | Yes | Yes |
| Can we access the data set through an alternate index? | Yes | Yes | No | No | No |
| What space used to insert records? | Space at the end of the dataset used | Free space is used for inserting and lengthening records | Empty slots are used | Free space is used for inserting and lengthening records | No record level processing |
| Is embedded free space defined? | No | Yes | No | No | No |
| Was spanned Records allowed? | Allowed | Allowed | No spanned records | No spanned records | No spanned records |
| Was Extended Format/Compression allowed? | Extended format allowed | Extended format or compression allowed | Extended format allowed | Extended format allowed | Extended format allowed |