The system logger component resides in its own address space, IXGLOGR,
on each system in a sysplex. Some of the component processing will
differ, depending on whether a given log stream is a coupling facility
log stream or a DASD-only log stream. The system logger component
does the following:
- Provides a set of system services that allows a system logger
application to use the system logger component.
See z/OS MVS Programming: Assembler Services Guide
and z/OS MVS Programming: Assembler Services Reference IAR-XCT for writing a system logger application.
- Maintains information in the LOGR policy about the current use
of log streams and if used, coupling facility list structures.
- For coupling facility log streams, system logger interacts with
cross-system extended services (XES) to connect to and use the coupling
facility for system logger applications.
- Obtains local storage buffer space. For a coupling facility log
stream, local storage buffers can be used for duplexing log data.
For a DASD-only log stream, local storage buffers are used as interim
storage for log data before it is off-loaded to DASD log data sets.
- Off-loads data to DASD log data sets as follows:
For
coupling facility log streams, system logger off-loads log data
from the coupling facility to DASD log data sets as the coupling facility
structure space associated with the log stream reaches the installation-defined
thresholds.
For DASD-only log streams,
system logger off-loads log data from the local storage buffers to
DASD log data sets as the DASD staging data set space reaches the
installation-defined thresholds.
- Automatically allocates new DASD log data sets for log streams.
- Maintains a backup copy of (duplexes) log data that is in interim
storage for recovery. Log data in interim storage is vulnerable to
loss due to system or sysplex failure because it has not yet been
hardened to DASD log data sets. System logger duplexes interim storage
log data for both coupling facility and DASD-only log streams.
- Produces SMF record type 88 for system logger accounting on a
single system. Record type 88 focuses on the usage of interim storage
(coupling facility or local storage buffers) and log stream data for
a system in the sysplex. Using the record can help an installation
avoid the STRUCTURE FULL or STAGING DATA SET FULL exceptions, and
perform other tuning and/or capacity planning analysis.
See z/OS MVS System Management Facilities (SMF)
for more record type 88 and system logger accounting. Sample program
IXGRPT1 in SYS1.SAMPLIB shows an example of producing a report from
SMF record type 88.
- Ensures that:
- Provides recovery support in the event of application, system,
sysplex, or coupling facility structure failure for coupling facility
log streams. (See System logger recovery for information about recovery
for DASD-only log streams.)