February 28, 2017
Recently while presenting a DB2 12 technical workshop, I discussed pre-migration requirements. One important consideration is the need to ensure that the current DB2 11 active logs are not greater than 4 GB. When the active logs are greater than 4 GB, DB2 11 will startup without a problem and ignore the portion of the log greater than 4GB; however, DB2 12 will not start when in V12R1M100 function mode.
During DB2 12 startup, if the active logs are greater than 4 GB, this message is displayed
csect-name ACTIVE LOG DATA SET DSN=dsname IS GREATER THAN 4 GB IN SIZE
During this discussion, I was asked how to determine if the logs are greater than 4 GB. This is documented in the DB2 12 installation and migration guide
To allocate a 4-GB log, specify one of these options:
Any one of these allocates 3.9997 GB.
Once function level 500 or higher is activated in DB2 12, DB2 supports as many as 93 active log data sets with a maximum size of 768 GB each. This limit provides up to 71,424 GB of active log space. (Double the space calculation for dual logging.) In many cases, fewer than the maximum number of data sets can be used; for instance, two data sets might be sufficient. However, the more log space you allocate, the larger a burst of insert, update and delete operations can be without causing performance problems.
Posted February 28, 2017 | Permalink