An unpartitioned table with no clustered index consists of a single doubly linked chain of database pages, so each insertion into the table uses the last page of the chain. The SAP ASE server holds an exclusive lock on the last page while it inserts the rows, blocking other concurrent transactions from inserting data into the table.
Partitioning a table with the partition clause of the alter table command creates additional page chains. Each chain has its own last page, which can be used for concurrent insert operations. This improves insert performance by reducing page contention. If the table is spread over multiple physical devices, partitioning also improves insert performance by reducing I/O contention while the server flushes data from cache to disk. For more information about partitioning tables for insert performance, see Controlling Physical Data Placement in Performance and Tuning Guide: Basics.