Reading log records

Reading Db2 log records is useful for diagnostic and recovery purposes.

This information discusses three approaches to writing programs that read log records.

Contents of the log
The log contains the information that is needed to recover the results of program execution, the contents of the database, and the Db2 subsystem. The log does not contain information for accounting, statistics, traces, or performance evaluation.
The physical structure of the log
The active log consists of VSAM data sets with certain required characteristics.
Reading log records with IFI
You can use the READA (read asynchronously) request of the instrumentation facility interface (IFI) to read log records into a buffer. Use the READS (read synchronously) request to read specific log control intervals from a buffer. You can use these requests online while Db2 is running.
Reading complete log data for the GDPS Continuous Availability with zero data loss solution
The GDPS® Continuous Availability with zero data loss solution provides disaster recovery with continuous availability in a z/OS® environment. When Db2 participates in a GDPS Continuous Availability with zero data loss environment, IFI applications issue READS calls for IFCID 0306 to a proxy data sharing group, and the proxy data sharing group captures log records from a source data sharing group. Before the IFI applications can do that, you need to modify your Db2 environment, and modify the IFI applications that capture log records.
Reading log records with OPEN, GET, and CLOSE
You can use the assembler language DSNJSLR macro to submit OPEN, GET, and CLOSE functions. Use this stand-alone method to capture log records that you cannot read with the instrumentation facility interface (IFI) when Db2 stops running.
Reading log records with the log capture exit routine
You can use the log capture exit routine to capture Db2 log data in real time. You can use this exit routine online while Db2 is running.
How RBA and LRSN values are displayed
Db2 12 always displays RBA and LRSN values in the 10-byte format. This 10-byte display is unrelated to migration of the catalog or directory, conversion of individual objects to EXTENDED format, or BSDS conversion. For recovery purposes, this 10-byte format is the preferred input format for Db2. When 10-byte RBA or LRSN values are specified as input to Db2, conversion to 6-byte format is performed internally as needed.

Parent topic: Operation and recovery