AutoCollect – Creating SNAPSHOT and System DELTA Rowsets › Process Snapshot Rowsets into Delta Rowsets

Process Snapshot Rowsets into Delta Rowsets

The AUTOCOLL OPTION=DELTACRE function processes snapshot rowsets into Delta rowsets. The function can be started at a specific point in time (in the snapshot database) and can be targeted to a specific MUFNAME. The function processes the values from two Snapshot rowsets from the same MUF instance execution (MUFNAME and MUF Enable time are the same) and create a Delta rowset with the following:

• Identity columns. These columns represent Delta rowset identification information.
• Fixed columns. These columns represent Delta identification that is built from non-counter snapshot columns.
• Calculated columns. These are columns that are built from the calculation of ending snapshot value minus beginning snapshot value.

The AutoCollect DELTA Database chapter provides the contents of each Delta table. The column information includes a column information flag that indicates if the column was built as part of the rowset identification, copied from the starting snapshot, copied from the ending snapshot or calculated by subtracting the beginning snapshot value from the ending snapshot value.

Once the Delta row is built, it is added into the appropriate DELTA table.

For each Delta period processed, the DELTACRE function adds one row to the BVM and BVD DELTA ratio tables. These tables represent selected information collected and summarized from matching rows found in the other DELTA tables.

Note: In most shops, the information from BVM and BVD is used to report system performance and the information in the other DELTA tables is used to drill down as needed.

A report is generated providing Delta row generation counts and any error information.

The generation of Delta rows can be done multiple times. All selected Snapshot rowsets are processed and the corresponding Delta rowsets are created.

The DELTACRE function attempts to add all newly built Delta rowsets. If a Delta rowset already exists with the same identifying columns, the new Delta rowset is ignored. The DELTACRE function report indicates the number of rowsets ignored as a duplicate. This ignore process prevents you from overlaying a previously created Delta rowset. If you determine that the rowset should be overlaid, you need to first delete the rowset using the Delta rowset delete function and then re-run the DELTACRE function.

The DELTACRE function validates the calculated values for each Delta row. Calculated columns cannot have a negative value. For example, while the I/O count for a given duration can be zero (that is no I/O was done), it cannot be a negative value. The DELTACRE function reports an error for any Delta rows that have a negative value and those rows are not added to the Delta rowset.

Delta rowsets are not automatically deleted. Therefore, if you remove a Snapshot rowset, the Delta rowset remains. You can use the AUTOCOLL OPTION=DELTADEL function to remove unwanted Delta rowsets.