xrmemcachesize Attribute

Purpose

The xrmemcachesize attribute defines a hard limit for space usage in the Exadata RDMA Memory Cache (XRMEM cache). The limit cannot be exceeded, even if the cache is not full.

Syntax

 ALTER IORMPLAN 
   dbplan=(( name=db_name, ... xrmemcachesize=number ... ) ... )

Usage Notes

You specify the value for xrmemcachesize in bytes. You can also use the suffixes M (megabytes), G (gigabytes), or T (terabytes) to specify larger values. For example, 300M, 150G, or 1T.
The value for xrmemcachesize must be at least 4 MB.
The xrmemcachelimit and xrmemcachesize attributes cannot be specified in the same directive.
The value for xrmemcachesize cannot be smaller than xrmemcachemin, if it is specified.
In an IORM plan, if the size of the XRMEM cache can accommodate all of the xrmemcachemin and xrmemcachesize allocations, then each xrmemcachesize definition represents a guaranteed space allocation.

However, you can use the xrmemcachesize attribute to over-provision space in the XRMEM cache. Consequently, if the XRMEM cache size cannot accommodate all of the xrmemcachemin and xrmemcachesize allocations, then only xrmemcachemin is guaranteed.
On Exadata X8M and X9M systems with Oracle Exadata System Software release 23.1.0, the persistent memory data accelerator, previously known as PMEM cache, is now called XRMEM cache.

For backward compatibility, on Exadata X8M and X9M systems, you can use pmemcachesize instead of xrmemcachesize in the ALTER IORMPLAN command. However, starting with Oracle Exadata System Software release 23.1.0, output from the LIST IORMPLAN command only displays xrmemcachesize.