Quiescing VM activity
Before you copy an environment with running VMs, you should reduce activity of running applications to a minimum, also known as “quiescing” the VM, to reduce the risk of file or database corruption.
Contents
Operating Systems
Here are some actions you can take to help make sure running VMs are copied successfully:
| Operating system | Recommended action |
|---|---|
| Windows | Make sure Windows Volume Shadow Copy Service is correctly configured. |
| Linux | Use Fsfreeze to freeze all data volumes, and then unfreeze them after the copy completes. |
| AIX | Use chfs -a freeze to freeze all data volumes, and then unfreeze them after the copy completes. |
| IBM i | IBM i has several degrees of quiescence for the operating system and integrated database. |
Databases
We recommend that you place running databases in read-only or backup mode. Refer to documentation about using storage-level snapshot technology for the installed database.
Examples:
These links are version specific.
Other Applications
Check the application documentation for details about backing up the application using external backup technologies, such as storage-level snapshots.
IBM i degrees of quiescence
The following are the degrees of quiescence for IBM i, from completely powered off (1) to fully active (5)
1 – Power down or vary-off the system
This is a completely quiescent state: All data is flushed to disk and nothing is active.
2 – Suspend activity
IBM i 7.2 and 7.3
CHGASPACT ASPDEV(*SYSBAS) OPTION(*SUSPEND) SSPTIMO(60) SSPTIMOACN(*END)
IBM i 7.4
CHGASPACT ASPDEV(*SYSBAS) OPTION(*SUSPEND) SSPTIMO(60) SSPTIMOACN(*END) SSPFRCWRT(*YES)
This is the most quiescent state without powering down the VM.
- Gets all transactions to commit boundaries.
- Prevents the start of new database I/O.
- Non-database I/O continues to flow.
After the copy operation completes
CHGASPACT ASPDEV(*SYSBAS) OPTION(*RESUME)
3 – Suspend activity for system and basic user ASPs
IBM i 7.2 and 7.3
CHGASPACT ASPDEV(*SYSBAS) OPTION(*SUSPEND) SSPTIMO(60) SSPTIMOACN(*CONT)
IBM i 7.4
CHGASPACT ASPDEV(*SYSBAS) OPTION(*SUSPEND) SSPTIMO(60) SSPTIMOACN(*CONT) SSPFRCWRT(*YES)
- Gets as many transactions as possible to commit boundaries.
- Long-running transactions may remain active.
- Non-database activity continues as normal.
After the copy operation completes
CHGASPACT ASPDEV(*SYSBAS) OPTION(*RESUME)
4 – Write changed ASP MYASP pages to disk
CHGASPACT OPTION(*FRCWRT)
- Flushes mainstore.
- Does not halt any transactions.
5 – Do nothing
This is the least quiescent and most risky state.
- Can lead to database corruption, which can cause extended recovery times as the database attempts repairs during IPL.