The systabstats table contains basic statistics for tables and indexes, including:
Number of data pages for a table, or the number of leaf level pages for an index
Number of rows in the table
Height of the index
Average length of data rows and leaf rows
Number of forwarded and deleted rows
Number of empty pages
Statistics to increase the accuracy of I/O cost estimates, including cluster ratios, the number of pages that share an extent with an allocation page, and the number of OAM and allocation pages used for the object
Stopping points for the reorg command so that it can resume processing
systabstats contains one row for each clustered index, one row for each nonclustered index, one row for each table without a clustered index, and one row for each partition. The storage for clustered index information depends on the locking scheme for the table:
For data-only-locked tables, systabstats stores an additional row for a clustered index.
For allpages-locked tables, the data pages are treated as the leaf level of the index, so the systabstats entry for a clustered index is stored in the same row as the table data.
The indid column for clustered indexes on allpages-locked tables is always 1.