IFCID 001 - Log Manager Data

Record Trace - IFCID 001 - Log Manager Data

The field labels shown in the following sample layout of Record Trace - IFCID 001 - Log Manager Data are described in the following section.

                                                  LOG MANAGER DATA
WRITE REQUEST-WAIT ..................:                    0   READ FROM OUTPUT BUFFER .............:                 4464
WRITE REQUEST-NO WAIT ...............:             20143583   READ FROM ACTIVE LOG ................:                57671
WRITE REQUEST-FORCE .................:               116271   READ FROM ARCHIVE LOG ...............:                    0
WRITE LOG BUFFER ....................:               265031   READ DELAY-TAPE VOLUME CONTENTION ...:                    0
WRITE I/O REQUESTS ..................:               696824   READ DELAY-UNAVAILABLE RESOURCE .....:                    0
WRITE BUFFER SCHEDULED-THRESHOLD ....:                24867   CI CREATED-ACTIVE LOG ...............:              1352938
WRITE BUFFER PAGED IN ...............:                    0   CI OFFLOADED ........................:              1347840
WAIT FOR UNAVAILABLE LOG BUFFER .....:                    0   CI WRITTEN ..........................:              3056832
TOTAL BSDS ACCESS REQUESTS ..........:               135311   CI SERIAL WRITE .....................:                    0
TOTAL CDDS ACCESS REQUESTS ..........:                    0
ARCHIVE READ  ALLOCATIONS ...........:                    0   LOOK-AHEAD TAPE VOL MOUNTS ATTEMPTED.:                    0
ARCHIVE WRITE ALLOCATIONS ...........:                  156   LOOK-AHEAD TAPE VOL MOUNTS SUCCEEDED.:                    0
TOTAL LOG SUSP TIME ASYNC DUPLEXING..:                    0   TOTAL ZHYPERLINKLOG WRITES...........:                    0
TOTAL SUSPENDS ASYNC DUPLEXING.......:                    0   TOTAL ZHYPERLINKLOG WRITE FAILED SYNC:                    0

QJSTLSUS ........:               190089  QJSTSPNN ........:                    0  QJSTSPNI ........:                    0
QJSTCLID ........:                    1  QJSTCL2 .........:              X'0000'
QJSTCLSN ........: X'00CAF11AE9A68B3F5A00'
QJSTAVAL ........:                X'00'																		

WRITE REQUEST-WAIT

The number of wait log write requests. Wait indicates that the log record is first written to the log buffer and then to the log data set.

Field Name: QJSTWRW

READ FROM OUTPUT BUFFER

The number of log reads satisfied from the output buffer.

Background and Tuning Information

This field, together with the reads satisfied from active log and reads satisfied from archive log (QJSTRACT and QJSTRARH) fields indicate how efficiently DB2 retrieves log records. Use these numbers to adjust the number of output buffers and the total active log capacity to maximize DB2 performance.

Field Name: QJSTRBUF

This is an exception field.

WRITE REQUEST-NO WAIT

The number of log write requests.

The log record is written asynchronously to the log buffer. The application does not wait for the record to be written to the log data set and regains control immediately.

Buffered log records are written to DASD when the buffer threshold is exceeded.

Field Name: QJSTWRNW

This is an exception field.

READ FROM ACTIVE LOG

The number of log reads satisfied from the active log data set.

Background and Tuning Information

This field, together with the reads satisfied from archive log and reads satisfied from output buffer fields, indicate how efficiently DB2 retrieves log records. Use these numbers to adjust the number of output buffers and the total active log capacity to maximize DB2 performance. Ideally, this value should be 0 or very small.

Field Name: QJSTRACT

This is an exception field.

WRITE REQUEST-FORCE

The number of force log write requests. Force indicates that the log record is written to the log buffer, forcing the buffer to be written to the log data set on DASD.

Field Name: QJSTWRF

This is an exception field.

READ FROM ARCHIVE LOG

The number of log reads satisfied from archive log data sets.

Field Name: QJSTRARY

This is an exception field.

WRITE LOG BUFFER

The number of calls to the log write routine. This does not represent the number of physical log I/Os.

Field Name: QJSTBFWR

READ DELAY-TAPE VOLUME CONTENTION

The number of read accesses that were delayed because of a tape volume contention when only one reader per tape is possible.

Background and Tuning Information

This field shows the number of agents forced to wait because a tape volume was already in use by another. If this number is not 0, increase the read tape units on the archive log data set parameters panel DSNTIPA.

Field Name: QJSTTVC

This is an exception field.

WRITE I/O REQUESTS

The total number of log-write I/O requests (such as media manager calls). This is the sum of the IFCID 038/039 pairs and includes both copy1 and copy2 active log data set writes.

Background and Tuning Information

This value should correspond to the active log write I/O activity in an RMF report.

Field Name: QJSTLOGW

READ DELAY-UNAVAILABLE RESOURCE

The number of read accesses delayed due to unavailable resources.

Background and Tuning Information

Generally, this can be due to insufficient tape units allocated. If this is so, reissue the SET ARCHIVE command and use a higher value for the count parameter. Another (although unlikely) cause is insufficient archive log read service task availability.

Field Name: QJSTWUR

This is an exception field.

WRITE BUFFER SCHEDULED-THRESHOLD

The number asynchronous log write requests made because the log write threshold was reached.

Background and Tuning Information

This counter is provided primarily for an internal check. It is recommended to use the default write threshold of 20 buffers.

Field Name: QJSTTHRW

CI CREATED-ACTIVE LOG

The number of active log output control intervals created.

Background and Tuning Information

Log records are placed sequentially in output log buffers, which are formatted as VSAM control intervals. The control intervals are written to a set of predefined DASD active log data sets, which are used sequentially and recycled.

The ratio of this field to write output log buffers should be low.

Rules of thumb:

The lower the value, the better. A high value indicates that too many I/Os are required for the number of log buffers created.

It is possible that WRTTHRSH is set too low. It is also possible that transactions could be arriving so infrequently that at commit time force requests are not queued and each force request is individually triggering an I/O of its log buffers.

Field Name: QJSTBFFL

WRITE BUFFER PAGED IN

The number of times an output log buffer had to be paged in before it could be initialized. The log-write latch is held at this point.

Background and Tuning Information

A nonzero value could indicate that the output log buffer size is too large, or there is insufficient real storage to back up the output log buffer size.

Field Name: QJSTBPAG

CI OFFLOADED

The number of control intervals (CIs) offloaded from the active log to the archive log.

Field Name: QJSTCIOF

WAIT FOR UNAVAILABLE LOG BUFFER

The number of waits caused by an unavailable output log buffer.

When DB2 wants to write a log record and the log buffer is not available, DB2 and the application must wait for an available log buffer.

Background and Tuning Information

Another possible cause is that the size of the write threshold might be too close to the size of the output buffer.

If this field is not 0, increase the number in the output buffer field on installation panel DSNTIPL to increase the number of output buffers or increase the size of the buffer.

Field Name: QJSTWTB

This is an exception field.

CI WRITTEN

The total number of log control intervals (CIs) written. This includes CI rewrites and both copy1 and copy2 active log data set writes. If a given CI is rewritten 5 times, this counter is incremented by 5.

Field Name: QJSTCIWR

TOTAL BSDS ACCESS REQUESTS

The number of BSDS access requests.

Field Name: QJSTBSDS

CI SERIAL WRITE

The number of serial log write I/O requests. A serial log write I/O request occurs when DB2 rewrites a log CI that was previously written as a partial CI, in a dual logging environment. This value includes COPY1 and COPY2 active log data set writes. The difference between WRITE I/O REQ and CI SERIAL WRITE gives the number of parallel log write I/O requests. Typically, the first CI in a list of one start I/O is written serially, and the remaining to both COPY1 and COPY2 active log data sets. This value is meaningful only when DB2 runs in dual active log mode.

Field Name: QJSTSERW

TOTAL CDDS ACCESS REQUESTS

Total CDDS access requests.

Field Name: QJSTCDDS

ARCHIVE READ ALLOCATIONS

The number of archive log read allocations.

It indicates the frequency of archive log open and close activity.

Background and Tuning Information

A high number indicates a need for more or larger active log data sets. This value should be small, ideally 0.

Field Name: QJSTALR

LOOK-AHEAD TAPE VOL MOUNTS ATTEMPTED

The number of look ahead (tape volume) mounts attempted.

Background and Tuning Information

This field and field QJSTLAMS (label LOOK-AHEAD MOUNT SUCCESSFUL) show the efficiency of look ahead for tape mounts.

Field Name: QJSTLAMA

ARCHIVE WRITE ALLOCATIONS

The number of archive log write allocations.

It indicates the frequency of archive log open and close activity.

Background and Tuning Information

A high number indicates a need for more or larger active log data sets. This value should be small, ideally 0.

Field Name: QJSTALW

LOOK-AHEAD TAPE VOL MOUNTS SUCCEEDED

The number of successful look-ahead (tape volume) mounts. It indicates the look-ahead mounting performance gains.

Background and Tuning Information

For maximum performance, this field and field QJSTLAMA (label LOOK-AHEAD MOUNT ATTEMPTED) should be equal. To find the number of failed attempts, subtract the value in this field from LOOK-AHEAD MOUNT ATTEMPTED. Too many failed attempts negate potential performance gains. This can be caused by not having enough tape units available. Issue the DISPLAY ARCHIVE command and note the current count value. Then issue the SET ARCHIVE command using a higher value for the count parameter.

Field Name: QJSTLAMS

TOTAL LOG SUSP TIME ASYNC DUPLEXING

Total time in microseconds XES suspended the log writer to update the secondary lock structure for asynchronous lock duplexing.

Field Name: QJSTDPXT

TOTAL ZHYPERLINKLOG WRITES

Total number of zhyperlinklog write I/O requests.

Field Name: QJSTSYCW

TOTAL SUSPENDS ASYNC DUPLEXING

Total number of suspends XES suspended the log writer to update the secondary lock structure for asynchronous lock duplexing.

Field Name: QJSTDPXN

TOTAL ZHYPERLINKLOG WRITE FAILED SYNC

Total number of zhyperlinklog write I/O requests which failed to be synchronous.

Field Name: QJSTSYCF

QJSTLSUS

This field is for IBM service use.

Field Name: QJSTLSUS

QJSTSPNN

This field is for IBM service.

Field Name: QJSTSPNN

QJSTSPNI

This field is for IBM service.

Field Name: QJSTSPNI

QJSTCLID

This field is for IBM service.

Field Name: QJSTCLID

QJSTCL2

This field is for IBM service.

Field Name: QJSTCL2

QJSTCLSN

This field is for IBM service.

Field Name: QJSTCLSN

QJSTAVAL

This field is for IBM service.

Field Name: QJSTAVAL