When users insert data into a data-only-locked heap table, Adaptive Server tracks page numbers where the inserts have recently occurred, and keeps the page number as a suggestion for future tasks that need space. Subsequent inserts to the table are directed to one of these pages. If the page is full, Adaptive Server allocates a new page and replaces the old hint with the new page number.
Blocking while many users are simultaneously inserting data is much less likely to occur during inserts to data-only-locked heap tables than in APL tables. When blocking does occur, Adaptive Server allocates a small number of empty pages and directs new inserts to those pages using these newly allocated pages as hints.
For datarows-locked tables, blocking occurs only while the actual changes to the data page are being written; although row locks are held for the duration of the transaction, other rows can be inserted on the page. The row-level locks allow multiple transaction to hold locks on the page.
There may be slight blocking on data-only-locked tables, because Adaptive Server allows a small amount of blocking after many pages have just been allocated, so that the newly allocated pages are filled before additional pages are allocated.
Conflicts during inserts to heap tables are greatly reduced for data-only-locked tables, but can still take place. If these conflicts slow inserts, try:
Switching to datarows locking, if the table uses datapages locking
Using a clustered index to spread data inserts
Partitioning the table, which provides additional hints and allows new pages to be allocated on each partition when blocking takes place
