Temporary Disk Requirements
dirtmp sub-directory of the Oracle GoldenGate installation
directory. When total cached transaction data exceeds the CACHESIZE
setting of the CACHEMGR parameter, Extract will begin writing cache
data to temporary files. The cache manager assumes that all of the free space on the
file system is available. This directory can fill up quickly if there is a large
transaction volume with large transaction sizes. To prevent I/O contention and
possible disk-related Extract failures, dedicate a disk to this directory. You can
assign a name to this directory with the CACHEDIRECTORY option of
the CACHEMGR parameter.
Note:
CACHEMGR is an
internally self-configuring and self-adjusting parameter. It is rare that this
parameter requires modification. Doing so unnecessarily may result in
performance degradation. It is best to acquire empirical evidence before opening
an Oracle Service Request and consulting with Oracle Support.
It is typically more efficient for the operating system to swap to disk
than it is for Extract to write temporary files. The default
CACHESIZE setting assumes this. Thus, there should be
sufficient disk space to account for this, because only after the value for
CACHESIZE is exceeded will Extract write transaction cached
data to temporary files in the file system name space. If multiple Extract processes
are running on a system, the disk requirements can multiply. Oracle GoldenGate
writes to disk when there is not enough memory to store an open transaction. Once
the transaction has been committed or rolled back, committed data is written to
trail files and the data are released from memory and Oracle GoldenGate no longer
keeps track of that transaction. There are no minimum disk requirements because when
transactions are committed after every single operation these transactions are never
written to disk.
Important:
Oracle recommends that you do not change the
CACHESIZE because performance can be adversely effected
depending on your environment.