OpenEdge Data Management: DataServer for Microsoft SQL Server

Connection pooling
Connection pooling
The DataServer for Microsoft SQL Server is enhanced with the ability to form a
connection pool. A connection pool is a set of database connections that are available
for an application to use and reuse without having to be reestablished. Connection
pooling significantly improves the cursor management associated with no-lock queries,
particularly multi-table joins. Creating and tearing down connections can be resource
intensive. Using a pooled connection to keep existing connections alive results in
significant performance gains because the DataServer avoids the overhead of making
a connection for each request. ABL applications that open multiple no-lock queries and
handle their results simultaneously experience the best cumulative performance gains
from connection pooling.
Main components
Connection pooling for the DataServer for Microsoft SQL Server is a combination of
ODBC connection pooling and DataServer connection management. These
connection components can be used as follows:
• Individually, ODBC connection pooling or DataServer connection management
provides the foundation required for firehose cursors, but enabling both provides
the best performance. For more information on firehose cursors, see the “Firehose
and Fast Forward-Only Cursors” section on page 164.
Without a connection pool, firehose cursors would block an application until a full
result set is retrieved. Because of this, when connection pooling is disabled,
firehose cursors are also disabled. By maintaining multiple connections and one
cursor per connection, read-only requests only block the connection on which they
retrieve results, freeing ABL applications to continue processing data on the other
connections.
• ODBC connection pooling and DataServer connection management provide the
highest performance improvements when enabled together, but they can also be
enabled independent of one another.
For installations where the number of ODBC connections is limited, you might
decide to enable only the DataServer connection management. For deployments
in which memory constraints are a concern, enabling only the ODBC connection
pool provides on-demand connections, with optimized resource efficiency. If both
an ODBC connection pool and managed connections coexist in the same
DataServer process, the managed connections will come from the ODBC
connection pool. The managed connections are distinguished from the connection
pool connections in that they are never released back to the pool for the life of an
ABL session.
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