IFCID 001 - Checkpoint and IFI Data

The IFCID 001 record block provides detailed information about checkpoint and IFI data.

CHECKPOINT AND IFI DATA
CHECKPOINT COUNT:          2  REASON STATISTICS INVOKED: ACTIVATED BY TIMER            HIGH USED RBA : X'00000000025056AE'
IFI ABENDS   :          0  IFI READA :          0  DCAP.LOG REC.RETRIEVED:          0  DCAP.DATA ROWS RETURNED:          0
IFI UNRECOG. :          0  IFI READS :          0  DCAP.LOG READS        :          0  DCAP.DATA DESC.RETURNED:          0
IFI COMMANDS :          0  IFI WRITE :          0  DCAP.LOG REC.RETURNED :          0  DCAP.DESCRIBES         :          0
DCAP.TABLES RETURNED   :          0
NO ROLLUP ACC RECS-ROLLUP THRESHOLD EXCEEDED   :          0    NO ROLLUP ACC RECS-ROLLUP STORAGE THRESHOLD EXC:          0
NO ROLLUP ACC RECS-STALENESS THRESHOLD EXCEEDED:          0    NO RECS NOT QUALIFIED FOR ACC ROLLUP           :          0

The fields shown in this record block are described below. Db2 field names are shown in brackets next to each report field.

CHECKPOINT COUNT [QWSDCKPT]

(Exception field) The number of checkpoints DB2® has taken. A checkpoint is a point at which Db2 records internal status information to the Db2 log. This information is used in the recovery process if Db2 abends.

Background and tuning information

For statistics reports only

A checkpoint is taken when the specified number of log records have been written. A checkpoint is also taken each time Db2 switches to a new active log data set. If the statistics reporting period is 30 minutes and the value of this field is 15, then Db2 is taking checkpoints every 2 minutes. If the data sets are too small or the value for LOGLOAD is too low, checkpoints occur too frequently. As a result, database writes do not perform efficiently. The frequency of Db2 checkpoints can be decreased by increasing the value of the DSNZPARM LOGLOAD (CHECKPOINT FREQ on the tracing install panel).

Rule of thumb

In a production environment, Db2 should take checkpoints approximately once every 10 minutes. The default value for LOGLOAD is 50000. The value you choose depends on the volume and nature of the work performed by your Db2 subsystem. It is a trade-off between the performance efficiency of larger numbers and the longer time to restart Db2 when there is an abnormal termination.

REASON STATISTICS INVOKED [QWSDRINV]

The reason the statistics records were written.

HIGH USED RBA [QWSDLRG] [QWSDLR prior to Db2 11]

The high-used RBA address of the log.

IFI ABENDS [QWSDSCA]

The number of instrumentation facility interface (IFI) abends.

IFI READA [QWSDSCRA]

The number of calls made to IFI using the READA (read asynchronous data) function.

DCAP.LOG REC.RETRIEVED [QWSDCDLC]

The number of log records retrieved for which data capture processing was invoked.

DCAP.DATA ROWS RETURNED [QWSDCDDR]

The total number of data capture data rows returned.

IFI UNRECOG. [QWSDSCU]

The number of calls made to IFI using a function that is not recognized by the interface.

IFI READS [QWSDSCRS]

The number of calls made to IFI using the READS (read synchronous data) function.

DCAP.LOG READS [QWSDCDLR]

The total number of data capture log reads for processing IFI reads requests for IFCID 185.

DCAP.DATA DESC.RETURNED [QWSDCDDD]

The total number of data capture describes performed. A data capture describe is the process of getting descriptive information about a Db2 table from the catalog.

IFI COMMANDS [QWSDSCCO]

The number of calls made to IFI using the COMMAND function.

IFI WRITE [QWSDSCWR]

The number of calls made to IFI using the WRITE function.

DCAP.LOG REC.RETURNED [QWSDCDRR]

The total number of data capture log records returned.

DCAP.DESCRIBES [QWSDCDMB]

The total number of data capture describes performed. A data capture describe is the process of getting descriptive information about a Db2 table from the catalog.

DCAP.TABLES RETURNED [QWSDCDTB]

The total number of data capture tables returned to the caller of the IFI reads call for IFCID 185.

NO ROLLUP ACC RECS-ROLLUP THRESHOLD EXCEEDED [QWSDARTH]

The number of roll-up accounting records written due to roll-up threshold exceeded.

NO ROLLUP ACC RECS-ROLLUP STORAGE THRESHOLD EXC [QWSDARSG]

The number of roll-up accounting records written due to roll-up accounting storage threshold exceeded.

NO ROLLUP ACC RECS-STALENESS THRESHOLD EXCEEDED [QWSDARST]

The number of roll-up accounting records written due to staleness threshold exceeded.

NO RECS NOT QUALIFIED FOR ACC ROLLUP [QWSDARIR]

The number of records that failed to qualify for accounting roll-up because all roll-up key fields are equal to NULL or because of NULL values that are not permitted.