Sybase 12.5.1, User Manual

Page: 38 / 210

Configuring multiple instances of Historical Server
24
Historical Server
When multiple instances of Historical Server use different home directories:
• The Historical Server instances can be started by different user accounts.
• The Historical Server instances use different control files.
• The recording sessions of one server are not visible to the others. For
example, the
hs_list
command, issued through
isql
, cannot access the
recording sessions defined by another Historical Server using a different
home directory.
When deciding whether multiple instances should use the same or different
home directories, consider these factors:
• Visibility of data – if users of the multiple instances need access to each
other’s recording session definitions, use the same home directory. If
sharing is undesirable, use different home directories. All input sessions to
a playback session must be in the same home directory.
• Visibility of status information – the
hs_status
command cannot
distinguish between multiple instances of Historical Server using the same
home directory. If this distinction is important to Historical Server
administration, use different home directories.
• Contention on the control file – if a large control file receives heavy access
from multiple users, different home directories may give better user
response time. Actions such as creating recording sessions and listing
information about recording sessions use the control file; recording
sessions themselves, when they are running, do not block other users from
the control file.
Configuring an additional Historical Server on UNIX platforms
To configure an additional Historical Server on UNIX platforms:
1 Copy the start-up script that you created for the original Historical Server.
Name the new file to reflect the name of the new Historical Server you
want to start.
2 Edit the start-up file, changing the parameters to the start-up command as
appropriate for the new instance of Historical Server. See “Setting
Historical Server start-up parameters” on page 20. Pay particular attention
to the
-D
parameter, which specifies the Historical Server home directory.
You must decide whether you want multiple instances of Historical Server
to share the same home directory or maintain separate ones.