6.172 TRANSMEMORY

Valid For

Extract for DB2 on z/OS

Description

Use the TRANSMEMORY parameter to control the amount of memory and temporary disk space available for caching uncommitted transaction data. Because Oracle GoldenGate sends only committed transactions to the target database, it requires sufficient system memory to store transaction data on the source system until either a commit or rollback indicator is received.

This parameter is for use with a DB2 database on z/OS database. For all other databases, use the CACHEMGR parameter.

About Memory Management With TRANSMEMORY

TRANSMEMORY enables you to tune the Oracle GoldenGate transaction cache size and define a temporary location on disk for storing data that exceeds the size of the cache. Options are available for defining the total cache size, the per-transaction memory size, the initial and incremental memory allocation, and disk storage space.

Transactions are added to the memory pool specified by RAM, and each is flushed to disk when TRANSRAM is reached. An initial amount of memory is allocated to each transaction based on INITTRANSRAM and is increased by the amount specified by RAMINCREMENT as needed, up to the maximum set with TRANSRAM. Consequently, the value for TRANSRAM should be evenly divisible by the sum of (INITTRANSRAM + RAMINCREMENT).

To view current TRANSMEMORY settings, use the VIEW REPORT command in GGSCI.

Special z/OS Considerations

On a z/OS system, the RAM option not only controls the total virtual memory allocation for all cached transactions, but also controls the size of the heap memory that is allocated during startup. The large default value prevents fragmentation within the virtual memory pool, but in some installations it could cause virtual memory to be wasted, especially if the applications primarily generate small transactions. Allocating a large amount of heap memory also can cause Extract to be unresponsive at startup until z/OS completes the allocation.

On z/OS, set RAM just large enough to hold enough transaction activity without affecting the performance of Extract. If set too low, it can cause Extract to write transaction data to disk, causing Extract to run more slowly and to consume disk space. You might need to do some testing to determine the optimal value.

Default

None

Syntax

TRANSMEMORY
[RAM size]
[TRANSRAM size]
[TRANSALLSOURCES size]
[INITTRANSRAM size]
[RAMINCREMENT size]
[DIRECTORY (directory, max_size, max_file_size)]

RAM size

Specifies the total amount of memory to use for all cached transactions. On z/OS this also is the initial amount of memory to allocate per transaction. The default is 200 megabytes. 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

TRANSRAM size

Specifies the total amount of memory to use for a single transaction. The default is 50 megabytes. 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

TRANSRAM should be evenly divisible by both INITTRANSRAM and RAMINCREMENT for optimal results.

TRANSALLSOURCES size

Specifies the total amount of memory and disk space to use for a single transaction. The default is 50% of total available memory (memory and disk). 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

INITTRANSRAM size

(NonStop system only) Specifies the initial amount of memory to allocate for a transaction. The default is 500 kilobytes. 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

RAMINCREMENT size

Specifies the amount of memory to increment when a transaction requires more memory. The default is 500 kilobytes. 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

DIRECTORY (directory, max_size, max_file_size)

Specifies temporary disk storage for transaction data when its size exceeds the maximum specified with TRANSRAM. You can specify DIRECTORY more than once.

The directory size specified with max_size and the file size specified with max_file_size must be greater than the size of the memory specified with RAM.

The names of the files that are created take one of the following formats, depending on the process type:

• group_trans_00001.mem takes the name of the group and indicates that an online process created the file.

• PID_trans_00001.mem takes the name of a process ID (PID) and indicates that a one-time process (specified with the SPECIALRUN parameter) created the file.

• group_thread#_00001.mem takes a group name and a thread number, indicating that a threaded Extract created the file.

directory

The fully qualified path name of a directory. The default is the dirtmp sub-directory of the Oracle GoldenGate directory.

max_size

The maximum size of all files in the directory. The default is 2 gigabytes. If the space specified is not available, then 75% of available disk space is used. Values 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

max_file_size

The maximum size of each file in the directory. The default is 200 megabytes. Values 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

Examples

Example 1   

The following example allows per-transaction memory to be incremented ten times before data is flushed to disk, once for the initial allocation specified with INITTRANSRAM and then nine more times as permitted by RAMINCREMENT.

TRANSMEMORY DIRECTORY(c:\test\dirtmp, 3000000000,
300000000), RAM 8000K, TRANSRAM 1000K, INITTRANSRAM 100K,
RAMINCREMENT 100K

Example 2   

The following is the same as the preceding example, but with the addition of a second directory.

TRANSMEMORY DIRECTORY(c:\test\dirtmp, 3000000000,
300000000), DIRECTORY (c:\test\dirtmp2, 1000000000,
5000000), RAM 8000K, TRANSRAM 1000K, INITTRANSRAM 100K,
RAMINCREMENT 100K