Neoview Query Guide (R2.2)

VQP uses a binary tree structure for query plans. When you display the same query plan in VQP,
the right (or inner) table is listed first in the plan.
Figure 2-2 Simple Nested Join Plan With ESP Parallelism
Regardless of the complexity of the query and resulting plan, the join plan contains right and
left operators. The right or inner table is displayed first:
Process Architecture For a Query
Several processes are required to execute a query plan. This information applies to query execution
plans obtained through VQP. You will find it helpful to understand the processes where operators
execute when you need to identify problems in queries.
• MXOSRVR is the ODBC server through which VQP connects. This process is also called the
master executor or root and controls the overall execution of the query. Each VQP user
connection is made through a separate MXOSRVR process.
• MXCMP is the Neoview compiler and compiles the query and generates the query execution
plan. A separate MXCMP process is dedicated to each ODBC server process.
• ESP (Executor Server Process) is a helper process used for parallel execution of a query. Each
query can have many ESPs with the maximum of 1 ESP per CPU per plan step. ESPs are
dedicated to an active ODBC server connection and then available for reuse. If the ODBC
connection is broken and another user connects to the ODBC server, the ESPs are available
to the new user.
• DAM (Data Access Manager) is a disk process manager that manages access to data for the
volume. DAM processes are shared among all active queries and are never dedicated
processes. One logical DAM is allocated per disk volume (implemented as a set of processes
per disk volume).
Each operator executes within a process, and some operators might execute in different processes.
For example, the join operators can execute in either the master executor or ESP process. Sorts
28 Using Visual Query Planner