EMS Manual

Configuring EMS
EMS Manual—426909-005
12-24
Collector Context
The primary collector must have a default subvolume in which to log event messages
when other subvolume information is not available or has not yet been provided. The
default subvolume is $SYSTEM.ZLOGnn.
The default subvolume is used to initialize the LOGSUBVOL attribute at system load; it
is also used when the current log subvolume becomes inaccessible because of a disk
problem. The default subvolume cannot be changed except by system loading from a
different system subvolume.
Alternate Collector Context
Each alternate collector maintains a context file in the subvolume where its log files are
kept. The name of this file is ZZEVCONF. If the log subvolume specified when an
alternate collector is started does not contain a file named ZZEVCONF, EMSCCTRL
creates this file and starts logging in the file ZZEV0000. If the file ZZEVCONF exists in
the specified log subvolume, and if it has a code of 843 (EMS log), the current log file
name specified in ZZEVCONF is used to determine the next log file. If the ZZEVCONF
file does not have a file code of 843, logging cannot start.
If a valid ZZEVCONF file exists when an alternate collector is started, the file is used to
determine the values of any attributes not specified as startup parameters.
BDS and PLF Information in the FILESWITCH Event
The ZZEVCONF context files contain a ZEMS-EVT-FILESWITCH event message that
includes the collector’s status at the time it last switched log files. This event message
includes status information about the collector’s pre-log filtration (PLF) and burst
detection and suppression (BDS) configurations and states. The states (ON or OFF) of
both PLF and BDS for the collector are contained in the ZEMS-MAP-COL-STATUS
token of ZEMS-EVT-FILESWITCH. BDS configuration values are contained in the
ZEMS-TKN-BDS-INFO token. The name of each PLF filter (if any exist) is contained in
its own ZEMS-TKN-XFILTERFILE token.
Unlike other fields in the FILESWITCH event, the current BDS and PLF states reflect
the state of the collector when the FILESWITCH event message was written, not
necessarily the correct BDS and PLF states for the log subvolume.
When the collector switches to an existing log subvolume, it assumes the log file
attributes that were recorded in the ZZEVCONF FILESWITCH event of that
subvolume. For example, if the EOFREFRESH field in the ZEMS-MAP-COL-STATUS
token of the event was set to ON, the collector runs with EOFREFRESH ON,
regardless of the state of EOFREFRESH before the log subvolume change.
However, BDS and PLF are considered process attributes rather than log file
attributes. Consequently, the states of both BDS and PLF remain constant in response
to subvolume switches.
Note. The LOGPREFIX keyword of the EMSACOLL program lets you rename the third
character in the prefix pattern of an alternate collector’s ZZEVCONF context file and
associated log files. For details, see EMSACOLL—Alternate Collector Program
on page 13-2.