OpenEdge Data Management: DataServer for Microsoft SQL Server

Tuning your environment with the –Dsrv startup parameter
SQL statements cache—the PRGRS_PREPCACHE option
The DataServer keeps a cache of prepared SQL statements that it reuses with new parameters.
This mechanism improves the DataServer performance. You can use the PRGRS_PREPCACHE
option to manage this cache in two ways:
• The MS SQL Server drivers are capable of re-using prepared statements and should do so
whenever possible. However, using -Dsrv PRGRS_PREPCACHE,0 instructs the DataServer
to re-prepare each SQL statement.
• Use the PRGRS_PREPCACHE option to control the size of the cache. The default cache size is
20 statements. You can increase the size for large applications that reuse many queries.
The maximum size depends on the amount of resources you have available.
Concurrent procedure results—the PRGRS_PROC_TRAN option
The DataServer allows only one active request for running a stored procedure. However, you
can process results form several stored procedures concurrently if you set the PRGRS_PROC_TRAN
switch to 1 (ON.) When switched on, this option will cause a separate connection to be used for
each stored procedure request, up to the maximum number of connections specified by the
PRGRS_CACHE_CONN option.
Caution: When procedures run in separate connections of the same DataServer session, the
scope of their respective transactions is isolated from one another. If one active
procedure attempts to update the same record used by another active procedure in the
same session, a lock timeout or even a deadlock could occur.
Cursor characteristics—the PRGRS_STABLE_CURS option
Enabling this switch indicates to the DataServer that it should assume that all cursors are stable.
Normally, the ODBC driver and MS SQL Server determines whether a cursor is stable during
the commit or rollback of a transaction and if the cursor can persist beyond a single transaction
scope. The DataServer normally resolves cursor characteristics by interrogating the driver and
setting the run-time environment accordingly.
Progress Software Corporation does not recommend bypassing normal operation under most
circumstances, but under very limited circumstances, you can improve performance by
overriding the derived cursor setting by setting the PRGRS_STABLE_CURS option to 1 (ON). Your
application must comply to one of the following restrictions to safely enable this option:
• All ABL run in your DataServer session is without transactions.
• ABL run in your DataServer session has transactions, but all ABL queries and resultant
data sets are fully processed on one side of any existing transaction boundary.
Note: This is a session-level switch, which means that all ABL run in the session must
comply with the listed restrictions.
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