What's "succession planning"? Why is it necessary?

Succession planning is a strategic HR term encorporating a large list of actions necessary to be initiated in all companies. Every responsible manager should worry about succession planning. Plainly explained it means that each manager should select a successor to take his position should he be promoted on a different position or should he leave the company.

Succession planning is normally initiated by HR who meets with all managers (in individual meetings)and together they go through the following steps:

1. The manager assesses his/her job and main tasks in a mature and responsible manner;
2. The manager appoints one person from his/her team to be the successor. The successor most of the time desn't know it. It's advisable to announce the decision to the successor only if we are talking about a very mature person. If not, the successor may end up following his manager around and watching his every step hoping that the position becomes vacant.
3. HR and the manager decide together upon a series of trainings and tasks that the successor needs to be involved in. Normally it is a medium to long term plan. The training doesn't happen in 2 weeks. It's a long process that can take even years.
4. The successor is gradually introduced to new tasks, shadowing his manager from time to time and participating in carefully planned training sessions.

More than one successor can be appointed and their evolution can be monitored over time to see which one is the best to be promoted in the end. Also, HR uses to split successors into categories depending on the amount of training and the time needed to be ready for the job. Several successors may be included in different categories - some ready in a few weeks, some in years.