Reduce client memory use

The memoryefficientbackup client option determines how much memory the client uses during incremental backup operations. Restricting the amount of memory that the client can use during incremental backups reduces the efficiency of incremental backup processing. The default setting for the memoryefficientbackup option is no, which does not limit the memory that the client can use.

During an incremental backup, the client determines which objects are new or changed since the last backup, and which objects must be expired on the server. An object, in this context, is a file or a directory.

By default, the client uses memory to create the list of new, changed, or expired objects to be updated by an incremental backup. Using available memory for this process makes incremental backups more efficient by reducing the time that is needed to prepare the list of objects to include in the backup. On client systems that have either limited memory, or that have applications that are not adversely affected if the client uses up the available memory, you can limit how much memory the client uses during incremental backups.

The following settings are available for the memoryefficientbackup option:

memoryefficientbackup no: The client uses an algorithm that does not limit the amount of memory that is used to process an incremental backup. This setting is the default, and it is the most efficient setting for incremental backups in many configurations.
memoryefficientbackup yes: The client uses an algorithm that requires less memory when it is processing incremental backups. This setting can increase the server workload, which, in turn, increases the time that is required to complete incremental backups. This setting can adversely affect incremental backup performance in configurations where there are many clients that are backing up files to the same server, and where each of the client systems has many file system objects.
memoryefficientbackup diskcachemethod: The client uses an algorithm that requires even less memory than memoryefficientbackup yes.; With this setting, the client keeps the list of objects to back up or expire on disk, so it uses less memory.

In many configurations, the most efficient setting for incremental backups is memoryefficientbackup no. However, if memory is limited on the client systems, or if you see IBM Spectrum Protect™ error messages that indicate memory errors, consider using a different setting. To determine the setting, review the following guidelines and select the first setting that applies:

```
memoryefficientbackup no
```
To determine whether you have enough memory to use memoryefficientbackup no, complete the following steps:
1. Determine the number of objects in the client file systems.
2. Round up the number of objects in the file systems, to the next million and divide that number by 1,000,000. Multiply the quotient by 300 MB to determine how to set the memoryefficientbackup option.
  For example, if the client file systems have 5,202,131 objects, round up this number to 6,000,000. Divide the result by 1 million and assign it to a temporary variable that is called numfsobjs. In this example, numfsobjs=6 (6,000,000/1,000,000=6). Use the value of numfsobjs as described in the following calculations:
  32-bit clients
  
  If the value of the numfsobjs variable is less than or equal to 5, multiply numfsobjs by 300 MB. If the amount of physical memory on the client system is equal to or greater than the product of numfsobjs x 300 MB, specify memoryefficientbackup no (the default).
  
  64-bit clients
  
  If the amount of physical memory on your client is equal to or greater than the product of numfsobjs x 300 MB, specify memoryefficientbackup no (the default).
```
memoryefficientbackup diskcachemethod
```
If the client has at least the following amount of fast, temporary disk storage available for use by the client process, specify memoryefficientbackup diskcachemethod.
- On UNIX and Linux systems, temporary disk space must meet or exceed numfsobjs x 300 MB.
- On Windows systems, temporary disk space must meet or exceed numfsobjs x 600 MB.
- On Mac OS X systems, temporary disk space must meet or exceed numfsobjs x 1200 MB.
If none of the previous conditions apply, use memoryefficientbackup yes.

Alternatives to using the memoryefficientbackup client option

To reduce client memory consumption, you can use the following alternatives instead of the setting memoryefficientbackup yes.

Use the client include and exclude options to back up only what is necessary.
Use journal-based incremental backup on Windows (NTFS), AIX® (JFS2), or Linux (all supported file systems) clients.
Use the virtualmountpoint option to define multiple virtual mount points within a single file system, and back up these mount points, sequentially. Virtual mount points can be used on UNIX and Linux systems, but not on Mac OS X.
Spread the data across multiple file systems and back up these file systems sequentially.
Use the image backup function to back up the entire volume. Image backups can take less time and resources than incremental backups, on file systems that have many small files.