Dbcc Memusage; Procedure Cache; Disk Subsystem Utilization, Monitoring And Optimization; Recovery Interval - Compaq 117755-003 - ProSignia - 740 Configuration Manual

Configuration and Tuning of Sybase System 11 for Microsoft Windows NT on Compaq Servers

Dbcc Memusage

Dbcc Memusage reports the following very useful information:
Y
Sybase SQL Server memory allocation at startup
Y
Memory used by 20 largest objects in the data cache
Y
Memory used by 12 largest stored procedures, triggers, views, rules and defaults in the

procedure cache

Run Dbcc Memusage occasionally to determine what is and what is not in the Sybase SQL Server
cache. Refer to the Sybase SQL Server System Administration Guide for more detailed
information on how to use this feature.
Procedure Cache
The amount of procedure cache you need for your stored procedures, triggers, views, rules and
defaults depends on their number and size. Keep in mind that multiple users accessing the same
stored procedure, for example, will cause Sybase SQL Server to store one copy of the same stored
procedure for each user.
Since reading stored procedures from disk to the procedure cache is costly, you want to keep all
needed stored procedures in the procedure cache. In other words, you want to prevent stored
procedures not in the procedure cache from pushing out those stored procedures already in cache
because your procedure cache is insufficient to hold them all.
Use Dbcc Memusage to monitor the 12 largest procedures in the procedure cache.
If you have more than 12 stored procedures in the procedure cache, Dbcc Memusage only shows
the 12 largest ones, and you will have to get a little creative to find out if you have enough
procedure cache. Below is an example.
1. Make a copy of one of your largest stored procedures, call it a different name, and execute it.
This step will place this stored procedure in the procedure cache. Use Dbcc Memusage to
verify this.
2. Execute the rest of your stored procedures, except for the one created in step 1, several times.
3. Use Dbcc Memusage to determine which 12 largest stored procedures remained in the
procedure cache. If you have enough procedure cache, your dummy stored procedure should
have remained in the list of top 12. If you don't have sufficient procedure cache, your
dummy stored procedure should have aged out and has been pushed out of the procedure
cache by other stored procedures.

Disk Subsystem Utilization, Monitoring and Optimization

This section provides information on parameters that you can set to influence performance from
the disk subsystem perspective and tools you have available to monitor the behavior of the
system.

Recovery Interval

Sybase SQL Server uses the recovery interval parameter to calculate how often to perform a
checkpoint. Sybase SQL Server internally computes the frequency of the checkpoint based on the
recovery interval value and the transaction rate to guarantee that in case of a system crash the
database(s) would be recovered within the time specified by the recovery interval parameter.
For example, in a heavy transaction processing environment, a recovery interval value of 5
(minutes) means that at the present transaction rate Sybase SQL Server would recover the
database within 5 minutes after restarting from a crash. Taking into consideration the present
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