Determining the Size of a Dump Device

The size required for a dump is not a constant value because the system does not dump paging space; only data that resides in real memory can be dumped. Paging space logical volumes will generally hold the system dump. However, because an incomplete dump may not be usable, follow the procedure below to make sure that you have enough dump space.

When a system dump occurs, all of the kernel segment that resides in real memory is dumped (the kernel segment is segment 0). Memory resident user data (such as u-blocks) are also dumped.

The minimum size for the dump space can best be determined using the sysdumpdev -e command. This gives an estimated dump size taking into account the memory currently in use by the system. If dumps are being compressed, then the estimate shown is for the compressed size of the dump, not the original size. In general, compressed dump size estimates will be much higher than the actual size. This occurs because of the unpredictability of the compression algorithm's efficiency. You should still ensure your dump device is large enough to hold the estimated size in order to avoid losing dump data.

sysdumpdev -e

If sysdumpdev -e returns the message, Estimated dump size in bytes: 9830400, then the dump device should be at least 9830400 bytes or 12MB (if you are using three 4MB partitions for the disk).