CACHEMGR
Valid For
Extract for all databases.
Description
Use the CACHEMGR
parameter to specify a non-default file system location for the temporary files needed to hold uncommitted transaction data. The CACHEMGR
parameter can also be used to control the amount of virtual memory and temporary disk space that is available for caching uncommitted transaction data. Both of these latter uses are discouraged.
Caution:
Do not change this parameter without consulting Oracle Support.CACHEMGR
is internally self-configuring and self-adjusting. 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.
However, you can specify the directory for the temporary files without assistance
Oracle GoldenGate only replicates committed transactions. Until a COMMIT
is received, any transactional data is stored in an area of virtual memory known as a cache. This cache is managed by the CACHEMGR
. If the amount of transaction data becomes too great for the virtual memory, then the CACHEMGR
writes some of the cached data to temporary files on disk.
Your systems should have sufficient operating system swap and page file space. Oracle recommends a minimum of 512GB.
Identifying the Paging Directory
By default, Oracle GoldenGate maintains the transaction data that it swaps to disk a sub-directory of the Oracle GoldenGate installation directory. CACHEMGR
assumes that all of the free space on the file system is available. This directory may fill up quickly if there is a large transaction volume with large transaction sizes. To prevent I/O contention and possible disk-related failures, dedicate a disk to this directory. You can assign directory location with the CACHEDIRECTORY
option of the CACHEMGR
parameter. A size can also be assigned. However, this is discouraged and should only be done after consulting Oracle Support.
Guidelines for Using CACHEMGR
-
This parameter is valid for all databases supported by Oracle GoldenGate.
-
At least one argument must be supplied.
CACHEMGR
by itself is invalid. -
Parameter options can be listed in any order.
-
Only one
CACHEMGR
parameter is permitted in a parameter file.
Default
None
Syntax
CACHEMGR { [CACHEDIRECTORY path [size] [, CACHEDIRECTORY path [size] [, ...],] CACHESIZE size }
-
CACHEDIRECTORY
path [size]
-
Specifies the name of the directory to which Oracle GoldenGate writes transaction data to disk temporarily when necessary. The default without this parameter is the
dirtmp
sub-directory of the Oracle GoldenGate installation directory. Any directory for temporary files can be on an Oracle Database file system, but cannot be on a direct I/O or concurrent I/O mounted file system that does not support themmap()
orMapViewOfFile()
system calls, like AIX.On Microservices Architecture (MA), the temporary file location is
$OGG_VAR_HOME/temp
.You can specify more than one directory by using a
CACHEDIRECTORY
clause for each one. The maximum number of directories is 100.The value can be specified in bytes or in terms of gigabytes, megabytes, or kilobytes in any of the following forms:
GB | MB | KB | G | M | K | gb | mb | kb | g | m | k
-
CACHESIZE
size
-
Sets a soft limit for the amount of virtual memory (
CACHESIZE
) that is available for caching transaction data. You can internally adjust theCACHESIZE
usingCACHEMGR
as necessary.If you feel that the default
CACHEMGR
configuration and internal self-adjustment is adversely affecting your system performance, then you should open a Service Request with Oracle Support. It is best to have acquired empirical data showing the problem symptoms in question to aid in configuring a new default.
Example
CACHEMGR CACHEDIRECTORY /net/d4atd/ggs/temp