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The Control‑M monitor can work in dual checkpoint mode. Under this mode, the Control‑M monitor maintains duplicate copies (mirror files) of the Control‑M Active Jobs file (CKP) and the IOA Conditions file (CND). If a disk crash makes the primary files inaccessible, they can be restored from the mirror files.
Note: For reasons of physical safety, both the mirror CKP and the CND must be placed on a different disk than the other Control‑M files. No dual checkpoint mode is available for the Control‑M Resources file (RES).
WARNING: Because of performance considerations, BMC no longer recommends using the mirror file mechanism. Instead—for backup and recovery—use the Control-M Journaling facility, described in Journaling. By using Journaling, you can avoid the performance loss associated with mirroring, taking advantage of the increased efficiency and integrity features built into modern storage devices.
The installation procedure for dual checkpoint mode is described in the explanation of ICE Step 4.2, "IOA Operational Parameters," and ICE Step 7, "Set Global Variables Database," in the IOA chapter of the INCONTROL for z/OS Installation Guide: Installing, and in the explanation of ICE Step 2, "Specify Control‑M Parameters," and ICE Step 3.1, "Control‑M Libraries and Repository," in the Control‑M chapter of the same guide.
When working in dual checkpointing mode, the Control‑M monitor keeps the Active Jobs mirror file synchronized with the primary Active Jobs file. The mirror file must be protected from any update by another source. If either the primary or mirror file becomes damaged, the Control‑M monitor shuts down with an appropriate message. To resume Control‑M monitor operation, the damaged file must be restored.
The Autoswitch feature can be enabled. If Dual Checkpointing is active, and the primary Active Jobs file undergoes hardware and software problems (in other words, is damaged), Control‑M automatically switches to dual. A message is issued, indicating that
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