Time stamping log and journal records

A local time change, forwards or backwards, has no effect on CICS® logging or journaling, or on CICS restarts, but could affect the operation of utility programs such as DFHJUP.

CICS time-stamps the data it writes to the system log as follows:

System log block headers are time-stamped with both the machine clock (STCK) value and local time
System log records are time-stamped with the machine clock (STCK) value only.

For general logs, in addition to time-stamping as in system logs, CICS also includes local time in the journal records.

During a restart, for system recovery purposes, CICS reads the youngest—most recently written—record from the primary log stream. Thereafter, CICS uses only direct reads using block ids and does not rely upon time stamps. CICS also uses direct read with block ids to retrieve the logged data for transaction backout purposes, again without any dependence on time stamps.

Operating a recovery process that is independent of time-stamps in the system log data ensures that CICS can restart successfully after an abnormal termination, even if the failure occurs shortly after local time has been put back.