Disk Store Operation Logs
At creation, each operation log is initialized at the disk store’s
max-oplog-size, with the size divided between the
drf files. When the oplog is closed, Pivotal GemFire shrinks the files to the space used in each file.
After the oplog is closed, GemFire also attempts to create a
krf file, which contains the key names as well as the offset for the value within the
crf file. Although this file is not required for startup, if it is available, it will improve startup performance by allowing GemFire to load the entry values in the background after the entry keys are loaded.
When an operation log is full, GemFire automatically closes it and creates a new log with the next sequence number. This is called oplog rolling. You can also request an oplog rolling through the API call
DiskStore.forceRoll. You may want to do this immediately before compacting your disk stores, so the latest oplog is available for compaction.
Note: Log compaction can change the names of the disk store files. File number sequencing is usually altered, with some existing logs removed or replaced by newer logs with higher numbering. GemFire always starts a new log at a number higher than any existing number.
This example listing shows the logs in a system with only one disk directory specified for the store. The first log (
BACKUPCacheOverflow_1.drf) has been closed and the system is writing to the second log.
bash-2.05$ ls -tlra total 55180 drwxrwxr-x 7 person users 512 Mar 22 13:56 .. -rw-rw-r-- 1 person users 0 Mar 22 13:57 BACKUPCacheOverflow_2.drf -rw-rw-r-- 1 person users 426549 Mar 22 13:57 BACKUPCacheOverflow_2.crf -rw-rw-r-- 1 person users 0 Mar 22 13:57 BACKUPCacheOverflow_1.drf -rw-rw-r-- 1 person users 936558 Mar 22 13:57 BACKUPCacheOverflow_1.crf -rw-rw-r-- 1 person users 1924 Mar 22 13:57 BACKUPCacheOverflow.if drwxrwxr-x 2 person users 2560 Mar 22 13:57 .
The system rotates through all available disk directories to write its logs. The next log is always started in a directory that has not reached its configured capacity, if one exists.
If no directory exists that is within its capacity limits, how GemFire handles this depends on whether automatic compaction is enabled.
If auto-compaction is enabled, GemFire creates a new oplog in one of the directories, going over the limit, and logs a warning that reports:
Even though the configured directory size limit has been exceeded a new oplog will be created. The current limit is of XXX. The current space used in the directory is YYY.
Note: When auto-compaction is enabled,
dir-sizedoes not limit how much disk space is used. GemFire will perform auto-compaction, which should free space, but the system may go over the configured disk limits.
If auto-compaction is disabled, GemFire does not create a new oplog, operations in the regions attached to the disk store block, and GemFire logs this error:
Disk is full and rolling is disabled. No space can be created