The following table shows the durability and performance tradeoffs for the commit protocols when journaling is enabled. If you do not require durability and if you are concerned primarily about performance then you would typically specify the commit local
option. While the commit safe
option is the only setting that guarantees durability, the remote
and region
settings provide progressively more protection from data loss if there is a database process failure.
Values for the |
Durability | Performance |
---|---|---|
safe
|
Guaranteed
None |
Fast Fastest |
region
|
||
remote
|
||
local
|
For information on the commit
database option, see Database Options.
You can use the commit
database option to specify one of the following types of commit protocols for Transaction Engines (TEs):
safe
local
remote[:n
]
region[:n
]
Note: The default protocol is safe
.
For each protocol, durability is a database transaction property that ensures that changes made during a transaction are persistent and can be re-created if a Storage Manager (SM) terminates and restarts. The following table describes each commit
option argument. See also Choosing a Commit Protocol.
safe
|
TE sends a pre-commit message to each SM serving a modified storage group of the committing transaction. The TE then receives a pre-commit acknowledgment from each SM, and sends a commit confirmation message to the client. See About the Safe Commit Protocol. |
local
|
TE sends a commit message to SM or SSM and does not wait for confirmation that the transaction was durably recorded. |
remote[:
|
Note: A modified storage group is a storage group in which the transaction has inserted, deleted, or updated data serviced by that storage group. For each modified storage group, this option specifies the number of SMs or SSMs that must confirm the transaction was durably recorded before the TE reports the transaction as committed. The TE waits for the specified number of confirmations before sending a commit confirmation to the client. If the optional |
region[:
|
For each modified storage group, this option specifies the number of regions that must confirm that the transaction was durably recorded before the TE reports the transaction as committed.
In this release, the If the optional
Consider the scenario in which there is one local region and two remote regions and It is possible for the local region to include SMs or SSMs that service some but not all of the modified storage groups. This means that SMs or SSMs in the local region can confirm that the transaction was durably recorded for only a subset of the modified storage groups. In this case:
If the |